fix(ai-term): stop F9 toggle shrinking the agent window each cycle

The F9 toggle captured the agent window's body-height and replayed it as
body-lines. Body-height subtracts the mode line's pixel height, which differs
between an active and an inactive mode line; the agent is captured active but
redisplayed inactive, so under a theme whose mode-line-inactive is shorter than
a text line the window lost ~1 line per toggle.

Capture and replay total-height for the vertical axis instead, via the renamed
cj/window-replay-size. Total-height is identical active or inactive and has no
mode-line-pixel dependence, so the round-trip is a fixed point. Width keeps
body-width (total-width has the position-dependent divider problem that total-
height does not). The shared lib fix covers the F12 terminal toggle too.

The shrink only manifests in a GUI frame, so it is not reproducible in the
batch harness; the unit tests pin the new total-height contract.

4 files changed, 31 insertions, 21 deletions

diff --git a/tests/test-ai-term--capture-state.el b/tests/test-ai-term--capture-state.el
index 543f83ad7..aa7421350 100644
--- a/tests/test-ai-term--capture-state.el
+++ b/tests/test-ai-term--capture-state.el
@@ -27,7 +27,9 @@
       (should (= cj/--ai-term-last-size (window-body-width right))))))
 
 (ert-deftest test-ai-term--capture-state-below-split-sets-direction ()
-  "Normal: below-split window -> direction=below, integer body-lines matching window."
+  "Normal: below-split window -> direction=below, integer total-lines matching window.
+The vertical axis captures total-height (not body-height) so the toggle
+round-trip is immune to the mode line's pixel height."
   (save-window-excursion
     (delete-other-windows)
     (let ((below (split-window (selected-window) nil 'below))
@@ -36,7 +38,7 @@
       (cj/--ai-term-capture-state below)
       (should (eq cj/--ai-term-last-direction 'below))
       (should (integerp cj/--ai-term-last-size))
-      (should (= cj/--ai-term-last-size (window-body-height below))))))
+      (should (= cj/--ai-term-last-size (window-total-height below))))))
 
 (ert-deftest test-ai-term--capture-state-noop-on-dead-window ()
   "Boundary: nil window -> state remains unchanged."
diff --git a/tests/test-cj-window-geometry-lib.el b/tests/test-cj-window-geometry-lib.el
index 938749f21..d32a48a92 100644
--- a/tests/test-cj-window-geometry-lib.el
+++ b/tests/test-cj-window-geometry-lib.el
@@ -2,7 +2,7 @@
 
 ;;; Commentary:
 ;; Tests the pure helpers in `cj-window-geometry-lib.el':
-;; `cj/window-direction', `cj/window-body-size',
+;; `cj/window-direction', `cj/window-replay-size',
 ;; `cj/cardinal-to-edge-direction', and `cj/window-at-edge'.
 
 ;;; Code:
@@ -52,30 +52,32 @@
     (delete-other-windows)
     (should (eq (cj/window-direction (selected-window) 'below) 'below))))
 
-(ert-deftest test-cj-window-geometry--body-size-right-returns-body-cols ()
+(ert-deftest test-cj-window-geometry--replay-size-right-returns-body-cols ()
   "Normal: right window with direction='right -> body-width in cols."
   (save-window-excursion
     (delete-other-windows)
     (let ((right (split-window (selected-window) nil 'right)))
-      (should (= (cj/window-body-size right 'right)
+      (should (= (cj/window-replay-size right 'right)
                  (window-body-width right))))))
 
-(ert-deftest test-cj-window-geometry--body-size-below-returns-body-lines ()
-  "Normal: below window with direction='below -> body-height in lines."
+(ert-deftest test-cj-window-geometry--replay-size-below-returns-total-lines ()
+  "Normal: below window with direction='below -> total-height in lines.
+The vertical axis captures total-height (not body-height) so the capture/
+replay round-trip is immune to the mode line's pixel height."
   (save-window-excursion
     (delete-other-windows)
     (let ((below (split-window (selected-window) nil 'below)))
-      (should (= (cj/window-body-size below 'below)
-                 (window-body-height below))))))
+      (should (= (cj/window-replay-size below 'below)
+                 (window-total-height below))))))
 
-(ert-deftest test-cj-window-geometry--body-size-narrow-window ()
+(ert-deftest test-cj-window-geometry--replay-size-narrow-window ()
   "Normal: deliberately narrow right window -> matching body cols."
   (save-window-excursion
     (delete-other-windows)
     (let* ((frame-w (frame-width))
            (target-cols (/ frame-w 4))
            (right (split-window (selected-window) (- target-cols) 'right)))
-      (should (= (cj/window-body-size right 'right)
+      (should (= (cj/window-replay-size right 'right)
                  (window-body-width right))))))
 
 (ert-deftest test-cj-window-geometry--cardinal-to-edge-right ()
diff --git a/tests/test-cj-window-toggle-lib.el b/tests/test-cj-window-toggle-lib.el
index 0762e255c..5edd06e96 100644
--- a/tests/test-cj-window-toggle-lib.el
+++ b/tests/test-cj-window-toggle-lib.el
@@ -36,7 +36,9 @@
                  (window-body-width right))))))
 
 (ert-deftest test-cj-window-toggle-capture-records-below-split ()
-  "Normal: below-split window writes direction=below and integer body-lines."
+  "Normal: below-split window writes direction=below and integer total-lines.
+The vertical axis captures total-height, not body-height, so the round-trip
+is immune to the mode line's pixel height (see `cj/window-replay-size')."
   (save-window-excursion
     (delete-other-windows)
     (let ((below (split-window (selected-window) nil 'below))
@@ -49,7 +51,7 @@
       (should (eq test-cj-window-toggle--last-direction 'below))
       (should (integerp test-cj-window-toggle--last-size))
       (should (= test-cj-window-toggle--last-size
-                 (window-body-height below))))))
+                 (window-total-height below))))))
 
 (ert-deftest test-cj-window-toggle-capture-falls-back-to-default-direction ()
   "Boundary: window filling the frame uses the supplied default direction."
@@ -156,7 +158,9 @@ transfer; clearing it lets the consumer's default size apply."
     (should (eq (cdr (assq 'inhibit-same-window received-alist)) t))))
 
 (ert-deftest test-cj-window-toggle-display-saved-maps-below-to-bottom ()
-  "Normal: saved below + integer size -> bottom edge, body-lines cons."
+  "Normal: saved below + integer size -> bottom edge, plain total-line count.
+The height axis replays a total-line integer (not a body-lines cons) so the
+round-trip is immune to the mode line's pixel height."
   (let (received-alist
         (test-cj-window-toggle--last-direction 'below)
         (test-cj-window-toggle--last-size 12))
@@ -169,8 +173,7 @@ transfer; clearing it lets the consumer's default size apply."
        'test-cj-window-toggle--last-size
        0.7))
     (should (eq (cdr (assq 'direction received-alist)) 'bottom))
-    (should (equal (cdr (assq 'window-height received-alist))
-                   '(body-lines . 12)))
+    (should (equal (cdr (assq 'window-height received-alist)) 12))
     (should-not (assq 'window-width received-alist))))
 
 (ert-deftest test-cj-window-toggle-display-saved-maps-right-to-rightmost ()
diff --git a/tests/test-term-toggle--display.el b/tests/test-term-toggle--display.el
index 7fa7f0a98..d6dd33da2 100644
--- a/tests/test-term-toggle--display.el
+++ b/tests/test-term-toggle--display.el
@@ -17,7 +17,9 @@
 (require 'term-config)
 
 (ert-deftest test-term-toggle--capture-state-records-direction-and-size ()
-  "Normal: capture-state writes direction and integer body size."
+  "Normal: capture-state writes direction and integer size.
+The vertical axis captures total-height (not body-height) so the toggle
+round-trip is immune to the mode line's pixel height."
   (save-window-excursion
     (delete-other-windows)
     (let ((below (split-window (selected-window) nil 'below))
@@ -26,7 +28,7 @@
       (cj/--term-toggle-capture-state below)
       (should (eq cj/--term-toggle-last-direction 'below))
       (should (integerp cj/--term-toggle-last-size))
-      (should (= cj/--term-toggle-last-size (window-body-height below))))))
+      (should (= cj/--term-toggle-last-size (window-total-height below))))))
 
 (ert-deftest test-term-toggle--capture-state-noop-on-dead-window ()
   "Boundary: nil window -> state remains unchanged."
@@ -50,7 +52,9 @@
     (should (eq (cdr (assq 'inhibit-same-window received-alist)) t))))
 
 (ert-deftest test-term-toggle--display-saved-maps-cardinal-to-edge ()
-  "Normal: saved 'below maps to bottom edge; integer size wraps in body-lines."
+  "Normal: saved 'below maps to bottom edge; integer size is a plain total-line count.
+The height axis replays a total-line integer (not a body-lines cons) so the
+round-trip is immune to the mode line's pixel height."
   (let (received-alist
         (cj/--term-toggle-last-direction 'below)
         (cj/--term-toggle-last-size 12))
@@ -58,8 +62,7 @@
                (lambda (_b a) (setq received-alist a) 'fake-window)))
       (cj/--term-toggle-display-saved 'fake-buf nil))
     (should (eq (cdr (assq 'direction received-alist)) 'bottom))
-    (should (equal (cdr (assq 'window-height received-alist))
-                   '(body-lines . 12)))
+    (should (equal (cdr (assq 'window-height received-alist)) 12))
     (should-not (assq 'window-width received-alist))))
 
 (ert-deftest test-term-toggle--display-saved-strips-conflicting-alist-entries ()