feat(startup): sync language bundles per project on session launch

Startup synced the .ai/ templates into the current project every session but never checked the language bundle (elisp, python) installed in .claude/. Bundle drift went unnoticed until someone re-ran make install-lang by hand: a generic rule added to claude-rules/ after the last install, or a changed validator hook.

scripts/sync-language-bundle.sh closes that gap. It fingerprints which bundle a project has by the presence of the language's own rule files (elisp.md, python-testing.md), then reconciles against the canonical source: auto-fix for rulesets-owned files (.claude/rules/*.md, .claude/hooks/*, githooks/*), surface-only for settings.json, which a project may have customized. CLAUDE.md is left alone. It's seed-only in install-lang and project-owned afterward, the same reason diff-lang skips it.

Startup Phase A step 12 calls it for the current project, guarded so older checkouts that lack the script still boot. It writes only under .claude/ and githooks/, disjoint from the .ai/ rsync paths, so the parallel batch stays safe. A script rather than a make target keeps the Makefile-parse layer off the boot path. The absolute rulesets path it depends on is the same one the rsyncs already carry.

Tested: 11 bats cases (no-bundle, clean, drifted rule/hook auto-fixed, surfaced settings.json asserted unmodified, absent CLAUDE.md not flagged, python detection, $PWD default, bad path). A smoke run against a copy of a real elisp project's .claude/ caught a perpetual "CLAUDE.md missing" alarm, which is what drove dropping CLAUDE.md from the surface set.

1 files changed, 142 insertions, 0 deletions

diff --git a/scripts/sync-language-bundle.sh b/scripts/sync-language-bundle.sh
new file mode 100755
index 0000000..8858f74
--- /dev/null
+++ b/scripts/sync-language-bundle.sh
@@ -0,0 +1,142 @@
+#!/usr/bin/env bash
+# Per-project language-bundle freshness check, designed to run at startup.
+#
+# Detects which language bundle(s) a project has by fingerprint (no marker
+# file), then reconciles them against the canonical rulesets source:
+#   - AUTO-FIX  (rulesets-owned, safe to overwrite): .claude/rules/*.md,
+#               .claude/hooks/*, githooks/*
+#   - SURFACE   (project may customize — reported, never written):
+#               .claude/settings.json
+# CLAUDE.md is intentionally not tracked: it is seed-only in install-lang
+# and project-owned afterward (diff-lang skips it for the same reason).
+#
+# Usage: sync-language-bundle.sh [project-path]    (default: $PWD)
+#
+# Exit: 0  no bundle, or clean / rules+hooks auto-fixed (resolved)
+#       3  manual action recommended (settings.json / CLAUDE.md drift)
+#       1  usage / path error
+#
+# Quiet when there is nothing to report. Resolves the canonical source
+# relative to its own location, so it always reads the current checkout.
+
+set -u
+
+PROJECT="${1:-$PWD}"
+
+REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+LANG_ROOT="$REPO_ROOT/languages"
+GENERIC_RULES="$REPO_ROOT/claude-rules"
+
+if [ ! -d "$PROJECT" ]; then
+  echo "ERROR: project path does not exist: $PROJECT" >&2
+  exit 1
+fi
+PROJECT="$(cd "$PROJECT" && pwd)"
+
+[ -d "$LANG_ROOT" ] || exit 0   # no bundles available — nothing to do
+
+OUT=""           # buffered report, printed once at the end
+FIXED=0
+MANUAL=0
+HEADER_DONE=0
+CUR_HEADER=""
+
+ensure_header() {
+  if [ "$HEADER_DONE" -eq 0 ]; then
+    OUT+="$CUR_HEADER"$'\n'
+    HEADER_DONE=1
+  fi
+}
+
+# fix SRC DST [exec] — overwrite DST from SRC if missing or differing.
+fix() {
+  local src="$1" dst="$2" want_exec="${3:-}"
+  [ -f "$src" ] || return 0
+  if [ ! -f "$dst" ] || ! diff -q "$src" "$dst" >/dev/null 2>&1; then
+    mkdir -p "$(dirname "$dst")"
+    cp "$src" "$dst"
+    [ "$want_exec" = exec ] && chmod +x "$dst"
+    ensure_header
+    OUT+="  fixed   ${dst#"$PROJECT"/}"$'\n'
+    FIXED=$((FIXED + 1))
+  fi
+}
+
+# surface SRC DST — report DST drift without writing.
+surface() {
+  local src="$1" dst="$2" reason=""
+  [ -f "$src" ] || return 0
+  if [ ! -f "$dst" ]; then
+    reason="missing"
+  elif ! diff -q "$src" "$dst" >/dev/null 2>&1; then
+    reason="differs"
+  else
+    return 0
+  fi
+  ensure_header
+  OUT+="  drift   ${dst#"$PROJECT"/} ($reason — not auto-fixed)"$'\n'
+  MANUAL=$((MANUAL + 1))
+}
+
+for src_lang in "$LANG_ROOT"/*/; do
+  [ -d "$src_lang" ] || continue
+  src_lang="${src_lang%/}"
+  lang="$(basename "$src_lang")"
+  lang_rules="$src_lang/claude/rules"
+  [ -d "$lang_rules" ] || continue
+
+  # Fingerprint: project has this bundle iff any of the language's own
+  # rule files is present in .claude/rules/.
+  detected=0
+  for rf in "$lang_rules"/*.md; do
+    [ -f "$rf" ] || continue
+    if [ -f "$PROJECT/.claude/rules/$(basename "$rf")" ]; then
+      detected=1
+      break
+    fi
+  done
+  [ "$detected" -eq 1 ] || continue
+
+  CUR_HEADER="language bundle '$lang' — $PROJECT:"
+  HEADER_DONE=0
+  manual_before=$MANUAL
+
+  # AUTO-FIX: generic rules (shared) + language rules
+  for f in "$GENERIC_RULES"/*.md; do
+    [ -f "$f" ] || continue
+    fix "$f" "$PROJECT/.claude/rules/$(basename "$f")"
+  done
+  for f in "$lang_rules"/*.md; do
+    [ -f "$f" ] || continue
+    fix "$f" "$PROJECT/.claude/rules/$(basename "$f")"
+  done
+
+  # AUTO-FIX: language hooks (executable)
+  if [ -d "$src_lang/claude/hooks" ]; then
+    while IFS= read -r f; do
+      rel="${f#"$src_lang"/claude/}"
+      fix "$f" "$PROJECT/.claude/$rel" exec
+    done < <(find "$src_lang/claude/hooks" -type f)
+  fi
+
+  # AUTO-FIX: githooks (executable)
+  if [ -d "$src_lang/githooks" ]; then
+    while IFS= read -r f; do
+      rel="${f#"$src_lang"/githooks/}"
+      fix "$f" "$PROJECT/githooks/$rel" exec
+    done < <(find "$src_lang/githooks" -type f)
+  fi
+
+  # SURFACE-ONLY: settings.json may carry project customization, so report
+  # rather than overwrite. (CLAUDE.md is intentionally untracked here — it's
+  # seed-only in install-lang and project-owned after, same as diff-lang skips it.)
+  surface "$src_lang/claude/settings.json" "$PROJECT/.claude/settings.json"
+
+  if [ "$MANUAL" -gt "$manual_before" ]; then
+    OUT+="  → reconcile: make install-$lang PROJECT=."$'\n'
+  fi
+done
+
+[ -n "$OUT" ] && printf '%s' "$OUT"
+[ "$MANUAL" -gt 0 ] && exit 3
+exit 0