refactor: extract toggle-state helpers shared by F9 and F12

The F12 commit (554b32d) flagged this as a follow-up: ~120 lines of capture-state and display-saved logic were duplicated between modules/ai-vterm.el and modules/eshell-vterm-config.el. The only differences were the default direction (right for F9, below for F12) and the customization name for the fallback size. Extract the shared logic into modules/cj-window-toggle.el so both consumers reduce to thin delegates that pass their state-var symbols and defaults. The state vars stay where they were, so existing tests against each consumer's helpers keep working.

10 new tests cover the parameterized helpers in isolation. All consumer tests still pass.

1 files changed, 13 insertions, 59 deletions

diff --git a/modules/ai-vterm.el b/modules/ai-vterm.el
index e817f441..482f6522 100644
--- a/modules/ai-vterm.el
+++ b/modules/ai-vterm.el
@@ -37,6 +37,7 @@
 (require 'cl-lib)
 (require 'seq)
 (require 'cj-window-geometry)
+(require 'cj-window-toggle)
 
 (declare-function vterm "vterm" (&optional buffer-name))
 (declare-function vterm-send-string "vterm" (string &optional paste-p))
@@ -235,15 +236,12 @@ cost of not auto-scaling if the frame itself resizes.")
 Sets `cj/--ai-vterm-last-direction' and `cj/--ai-vterm-last-size'
 so a subsequent F9 display can restore the user's chosen orientation
 and size.  Called at toggle-off (just before the window is torn
-down).  The default direction is 'right -- the module's side-panel
-default.
-
-Does nothing when WINDOW is not live."
-  (when (window-live-p window)
-    (let* ((dir (cj/window-direction window 'right))
-           (size (cj/window-body-size window dir)))
-      (setq cj/--ai-vterm-last-direction dir
-            cj/--ai-vterm-last-size size))))
+down).  The default direction is `right' -- the module's side-panel
+default.  Does nothing when WINDOW is not live."
+  (cj/window-toggle-capture-state
+   window 'right
+   'cj/--ai-vterm-last-direction
+   'cj/--ai-vterm-last-size))
 
 (defun cj/--ai-vterm-reuse-existing-claude (buffer _alist)
   "Display-buffer action: reuse any window in this frame already showing
@@ -268,56 +266,12 @@ project changes."
 (defun cj/--ai-vterm-display-saved (buffer alist)
   "Display-buffer action: split per saved direction and size.
 
-Reads `cj/--ai-vterm-last-direction' and `cj/--ai-vterm-last-size'
-(falling back to right and `cj/ai-vterm-window-width' when nil) and
-delegates to `display-buffer-in-direction' with an alist that carries
-the saved values.
-
-The captured cardinal direction (right/left/below/above) is mapped
-to its frame-edge variant (rightmost/leftmost/bottom/top) so the new
-claude always lands at the same frame edge it came from.  This
-means: the new window splits the frame's main window at the
-matching edge, not whatever window happens to be selected when F9
-fires.  Without this mapping, a toggle-off-on cycle in a 3+ window
-layout would put claude into a middle position (right of the
-selected window) rather than the edge it lived on before.  As a
-side benefit, claude always lands without a sibling on its
-captured-edge side, so its body-width and total-width match -- no
-divider chrome eating 1 col per toggle.
-
-An integer size (the captured absolute body-cols or body-lines) is
-wrapped in a `(body-columns . N)' / `(body-lines . N)' cons so
-`display-buffer-in-direction' sets the body width or body height
-exactly.  A float size (the customizable default fallback) passes
-through as a fraction of the new window's parent.
-
-Any direction/window-width/window-height entries in ALIST are
-stripped so the saved-state values control placement -- callers
-shouldn't specify direction or size in the rule when this action is
-used."
-  (let* ((direction (or cj/--ai-vterm-last-direction 'right))
-         (edge-direction (or (cj/cardinal-to-edge-direction direction)
-                             'rightmost))
-         (size (or cj/--ai-vterm-last-size cj/ai-vterm-window-width))
-         (size-key (if (memq direction '(right left))
-                       'window-width
-                     'window-height))
-         (body-tag (if (memq direction '(right left))
-                       'body-columns
-                     'body-lines))
-         (size-value (if (integerp size)
-                         (cons body-tag size)
-                       size))
-         (filtered (cl-remove-if
-                    (lambda (cell)
-                      (memq (car-safe cell)
-                            '(direction window-width window-height)))
-                    alist))
-         (effective (append
-                     (list (cons 'direction edge-direction)
-                           (cons size-key size-value))
-                     filtered)))
-    (display-buffer-in-direction buffer effective)))
+Delegates to `cj/window-toggle-display-saved' against the F9 state
+vars, falling back to `right' and `cj/ai-vterm-window-width'."
+  (cj/window-toggle-display-saved
+   buffer alist
+   'cj/--ai-vterm-last-direction 'right
+   'cj/--ai-vterm-last-size cj/ai-vterm-window-width))
 
 (defun cj/--ai-vterm-display-rule-list ()
   "Return the `display-buffer-alist' entry list installed by this module.