feat(theme-studio): color-families export round-trip and README close-out

Export stays a flat palette and import needs no reconstruction, because families are derived from the hex every render rather than stored. A #roundtriptest gate confirms export to import to export is byte-identical, and that the exported palette is still a flat [hex, name] list. Package seeding is unaffected since it reads the same flat palette.

The spec's planned ramp-step warning exemption is dropped after analysis: a generated ramp's steps are a stepL apart, well above the too-similar ΔE threshold, so they never trigger the warning, and exempting same-family pairs would hide genuine near-duplicates that should be flagged (the case #deltatest checks). So the warning stays on the full palette.

README documents color families: the hue grouping and its limitation, the ground strip, the per-column count control and regenerate, removed-step references reading "(gone)", and the removal of the standalone ramp panel. Phase 6, the last phase; the color-families v1 build is code-complete.

4 files changed, 72 insertions, 28 deletions

diff --git a/scripts/theme-studio/README.md b/scripts/theme-studio/README.md
index a2eb59b2..caee7b24 100644
--- a/scripts/theme-studio/README.md
+++ b/scripts/theme-studio/README.md
@@ -42,8 +42,9 @@ The runner regenerates the page, runs the Python templating tests
 (`test-colormath.mjs`, including the inline-integrity check), a syntax check of
 the spliced page script, and the browser hash gates in headless Chrome
 (`#selftest`, `#cursortest`, `#readouttest`, `#deltatest`, `#oklchtest`,
-`#planetest`, `#locktest`, `#sorttest`, `#mocktest`, `#ramptest`,
-`#contrasttest`, `#safetest`). It exits non-zero on any failure. The browser gates need a
+`#planetest`, `#locktest`, `#sorttest`, `#mocktest`, `#contrasttest`,
+`#safetest`, `#healtest`, `#familytest`, `#counttest`, `#baseedittest`,
+`#roundtriptest`). It exits non-zero on any failure. The browser gates need a
 Chromium-family browser; without one they report SKIPPED rather than passing
 silently. The pure color math and the extracted picker logic (`planeCell`,
 `paletteWarnings`) live in `colormath.js` so they are unit-tested directly in
@@ -66,10 +67,11 @@ Node; the DOM glue is covered by the browser hash gates.
 
 Three tiers of faces, plus the palette:
 
-- **Palette** — named colors. Add by hex or with the in-page color picker
+- **Palette** — named colors, shown grouped into hue *families* (see Color
+  families below). Add by hex or with the in-page color picker
   (saturation/value square, hue slider, palette reuse chips, live contrast
-  readout, and an any / AA+ / AAA legibility mask). Remove, rename, reorder with
-  arrows or drag. The colors serving as background and foreground are locked.
+  readout, and an any / AA+ / AAA legibility mask). Remove and rename per chip;
+  the colors serving as background and foreground are locked.
 
   The picker also shows perceptual readouts beside the WCAG ratio: the OKLCH
   coordinates (lightness, chroma, hue°) and the APCA Lc contrast against the
@@ -93,28 +95,42 @@ Three tiers of faces, plus the palette:
   per face, shown in a live mock Emacs buffer.
 - **Package faces** — per-package face tables with a live preview (below).
 
-## Ramps and background-contrast safety
-
-Two coupled features help build a harmonized palette and keep background tints
-readable. Both work in OKLCH, where lightness, chroma, and hue move
-independently. The pure math is in `app-core.js` (`ramp`, `fgSetFor`, `floor`,
-`lMax`); the DOM is in `app.js`.
-
-**Ramps.** The "ramp" button on the palette controls generates a tonal ramp from
-the current color: lighter and darker steps on a held hue, with the chroma easing
-out toward the extremes. Three controls set the shape, with defaults that produce
-a sensible first ramp:
-
-- `steps` — how many steps each direction (default 2, range 1-4).
-- `stepL` — the OKLCH lightness delta per step (default 0.08, range 0.04-0.12).
-- `chroma ease` — how much chroma drops at the farthest step (default 0.5, range
-  0-1; 0 holds chroma flat, 1 fully desaturates the last step).
-
-Each previewed step is named after the source swatch (`blue` gives `blue+1`,
-`blue-1`) and shows a clamp badge when it left the sRGB gamut. Click a step to
-add it, or "add all"; steps insert next to the source in order. A name that
-already exists is skipped (never overwritten); a generated hex that matches
-another entry is added but flagged as a duplicate.
+## Color families
+
+The palette is displayed as **families**: colors grouped into vertical columns by
+their actual color, dark at the top and light at the bottom, columns arranged left
+to right. Grouping is derived from the hex on every render — never from the name —
+so renaming a color to anything never moves it between columns. The flat palette
+underneath is unchanged (export stays a flat `[hex, name]` list); families are a
+view over it, and the per-chip rename/remove still work.
+
+- **Grouping.** Chromatic colors bucket by their nearest perceptual hue (red,
+  orange, yellow, green, teal, blue, purple, pink). Near-neutrals — grays, the
+  background and foreground ramps — collapse into one neutral column ordered by
+  lightness, using a lightness-scaled chroma threshold so a faint pale tint keeps
+  its hue while a faint mid gray reads as neutral. Columns sort by hue; the ground
+  strip (the `bg` and `fg` assignments) pins first, neutrals next. (Hue-adjacent
+  warm colors like olive-greens and golds can still share a column — a known
+  limitation, since by hue they really are adjacent.)
+- **The count control** under each chromatic column sets how many steps sit on
+  each side of the family's base (its most-saturated color). Setting N regenerates
+  the family as a symmetric base ±N tonal ramp via `ramp()` — lighter and darker
+  steps on the base's hue with chroma easing toward the extremes — *replacing* the
+  column's current colors. N=0 collapses to the base alone.
+- **Editing a base** recolors the whole family: change a base color and the family
+  regenerates from it at the same count.
+- **References follow.** When a regenerate changes a step's hex, any face assigned
+  to that step is re-pointed to the new hex. A step *removed* by lowering the count
+  leaves its references showing "(gone)" — visible and recoverable, never a silent
+  jump to a different color.
+
+The standalone ramp generator is gone; fanning a color into a ramp is now "add the
+color, then raise its column's count."
+
+## Background-contrast safety
+
+Keep background tints readable. Works in OKLCH; the pure math is in `app-core.js`
+(`fgSetFor`, `floor`, `lMax`), the DOM in `app.js`.
 
 **Worst-case contrast.** A background overlay sits behind many foregrounds at
 once, so one fg/bg contrast pair is the wrong number. For the covered overlay
diff --git a/scripts/theme-studio/app.js b/scripts/theme-studio/app.js
index 2680c084..92eec644 100644
--- a/scripts/theme-studio/app.js
+++ b/scripts/theme-studio/app.js
@@ -198,6 +198,9 @@ function renderPalette(){
     else{const tc=textOn(g.hex),sw=document.createElement('div');sw.className='pchip';sw.style.background=g.hex;sw.title=(g.role||'')+' '+g.hex;
       sw.innerHTML=`<input class="nm" value="${g.role||''}" disabled style="color:${tc}"><div class="hx" style="color:${tc}">${g.hex}</div>`;gs.appendChild(sw);}
   });
+  // The too-similar warning stays on the full flat palette: a generated ramp's
+  // steps are a stepL apart (well above the warning's ΔE threshold), so they never
+  // trigger it, and any pair that does is a genuine near-duplicate worth flagging.
   sortFamilies(families).forEach(f=>{
     const s=strip(f.neutral?' neutral':'');s.dataset.family=f.base;
     f.members.forEach(m=>{const i=idxOf(m.hex,m.name);if(i>=0)s.appendChild(paletteChip(i,nearest));});
@@ -1163,3 +1166,14 @@ if(location.hash==='#baseedittest'){let ok=true;const notes=[];const A=(c,n)=>{i
  PALETTE=saveP;for(const k in MAP)delete MAP[k];Object.assign(MAP,saveM);for(const f in UIMAP)delete UIMAP[f];Object.assign(UIMAP,saveU);selectedIdx=saveSel;renderPalette();
  document.title='BASEEDITTEST '+(ok?'PASS':'FAIL');
  const d=document.createElement('div');d.id='baseedittest';d.textContent='BASEEDITTEST '+(ok?'PASS':'FAIL')+(notes.length?' | '+notes.join(' ; '):'');document.body.appendChild(d);}
+// Round-trip gate (open with #roundtriptest): export stays a flat palette and
+// import needs no family reconstruction, so export → import → export is identical.
+if(location.hash==='#roundtriptest'){let ok=true;const notes=[];const A=(c,n)=>{if(!c){ok=false;notes.push(n);}};
+ const before=JSON.stringify(exportObj());
+ applyImported(before);
+ const after=JSON.stringify(exportObj());
+ A(before===after,'export → import → export is byte-identical');
+ const obj=JSON.parse(after);
+ A(Array.isArray(obj.palette)&&obj.palette.every(e=>Array.isArray(e)&&e.length===2),'exported palette is still a flat [hex,name] list');
+ document.title='ROUNDTRIPTEST '+(ok?'PASS':'FAIL');
+ const d=document.createElement('div');d.id='roundtriptest';d.textContent='ROUNDTRIPTEST '+(ok?'PASS':'FAIL')+(notes.length?' | '+notes.join(' ; '):'');document.body.appendChild(d);}
diff --git a/scripts/theme-studio/run-tests.sh b/scripts/theme-studio/run-tests.sh
index 44990588..2f46602c 100755
--- a/scripts/theme-studio/run-tests.sh
+++ b/scripts/theme-studio/run-tests.sh
@@ -53,7 +53,7 @@ CHROME=""
 for c in google-chrome-stable google-chrome chromium chromium-browser; do
   if command -v "$c" >/dev/null 2>&1; then CHROME="$c"; break; fi
 done
-HASHES="selftest cursortest readouttest deltatest oklchtest planetest locktest sorttest mocktest contrasttest safetest healtest familytest counttest baseedittest"
+HASHES="selftest cursortest readouttest deltatest oklchtest planetest locktest sorttest mocktest contrasttest safetest healtest familytest counttest baseedittest roundtriptest"
 if [ "$NO_BROWSER" = 1 ]; then
   skip_msg "browser hash gates (--no-browser)"
 elif [ -z "$CHROME" ]; then
diff --git a/scripts/theme-studio/theme-studio.html b/scripts/theme-studio/theme-studio.html
index 7d2f7b05..1a0b72c7 100644
--- a/scripts/theme-studio/theme-studio.html
+++ b/scripts/theme-studio/theme-studio.html
@@ -807,6 +807,9 @@ function renderPalette(){
     else{const tc=textOn(g.hex),sw=document.createElement('div');sw.className='pchip';sw.style.background=g.hex;sw.title=(g.role||'')+' '+g.hex;
       sw.innerHTML=`<input class="nm" value="${g.role||''}" disabled style="color:${tc}"><div class="hx" style="color:${tc}">${g.hex}</div>`;gs.appendChild(sw);}
   });
+  // The too-similar warning stays on the full flat palette: a generated ramp's
+  // steps are a stepL apart (well above the warning's ΔE threshold), so they never
+  // trigger it, and any pair that does is a genuine near-duplicate worth flagging.
   sortFamilies(families).forEach(f=>{
     const s=strip(f.neutral?' neutral':'');s.dataset.family=f.base;
     f.members.forEach(m=>{const i=idxOf(m.hex,m.name);if(i>=0)s.appendChild(paletteChip(i,nearest));});
@@ -1772,4 +1775,15 @@ if(location.hash==='#baseedittest'){let ok=true;const notes=[];const A=(c,n)=>{i
  PALETTE=saveP;for(const k in MAP)delete MAP[k];Object.assign(MAP,saveM);for(const f in UIMAP)delete UIMAP[f];Object.assign(UIMAP,saveU);selectedIdx=saveSel;renderPalette();
  document.title='BASEEDITTEST '+(ok?'PASS':'FAIL');
  const d=document.createElement('div');d.id='baseedittest';d.textContent='BASEEDITTEST '+(ok?'PASS':'FAIL')+(notes.length?' | '+notes.join(' ; '):'');document.body.appendChild(d);}
+// Round-trip gate (open with #roundtriptest): export stays a flat palette and
+// import needs no family reconstruction, so export → import → export is identical.
+if(location.hash==='#roundtriptest'){let ok=true;const notes=[];const A=(c,n)=>{if(!c){ok=false;notes.push(n);}};
+ const before=JSON.stringify(exportObj());
+ applyImported(before);
+ const after=JSON.stringify(exportObj());
+ A(before===after,'export → import → export is byte-identical');
+ const obj=JSON.parse(after);
+ A(Array.isArray(obj.palette)&&obj.palette.every(e=>Array.isArray(e)&&e.length===2),'exported palette is still a flat [hex,name] list');
+ document.title='ROUNDTRIPTEST '+(ok?'PASS':'FAIL');
+ const d=document.createElement('div');d.id='roundtriptest';d.textContent='ROUNDTRIPTEST '+(ok?'PASS':'FAIL')+(notes.length?' | '+notes.join(' ; '):'');document.body.appendChild(d);}
 </script>
\ No newline at end of file