feat(ai-vterm): F9 toggle/redisplay/pick + persistent split geometry

F9 was a single command that always opened the project picker. Three small frustrations stacked up. With one claude buffer open and not visible, F9 was a redundant prompt to pick a project that already had a session. With claude visible, there was no way to bury it without M-x quit-window. With two projects' buffers alive, swapping between them was a buffer-switch chore.

F9 is now a dispatch:

- Claude visible in this frame: quit the window (toggle off) and capture the geometry first.
- Exactly one claude buffer alive but hidden: re-display it (DWIM single-buffer case).
- Zero or two-plus alive: fall through to the project picker.

C-F9 is the always-pick-project entry point for explicit project switches. M-F9 is a buffer picker over the alive claude buffers. If a claude window is currently shown, the picked buffer replaces it in that window so the split orientation and size carry over. The shown buffer sorts last in the picker with a [shown] marker so RET picks "the other one."

Split geometry persists across toggles. Two module-level vars (cj/--ai-vterm-last-direction, cj/--ai-vterm-last-size) capture at toggle-off and feed a custom display action. After M-S-t flips claude from right to bottom, F9 toggle-off-then-on returns it at the bottom. After a mouse resize, the next toggle restores that fraction. State is per-session. Restarts reset to default right/0.5.

Two display-buffer fixes came out of testing:

- save-window-excursion around (vterm name) keeps the dashboard from being buried on a fresh F9 at startup. vterm calls pop-to-buffer-same-window internally, which would otherwise replace the selected window's buffer before the alist could route the new one.
- The action chain swaps display-buffer-use-some-window for a more specific cj/--ai-vterm-reuse-existing-claude. The generic version stole non-claude windows on C-F9 when the user was focused inside claude (claude on bottom, code on top -> new project landed in the code window). The specific version only reuses windows that already show a claude buffer.

I reclaimed C-F9 from the gptel toggle in ai-config.el. C-; a t still binds gptel.

I added eight new test files (claude-buffers, displayed-claude-window, dispatch, pick-buffer-candidates, window-geometry, capture-state, display-saved, reuse-existing-claude) plus a regression test on cj/--ai-vterm-show-or-create for the dashboard-preservation fix. All 73 ai-vterm tests pass and the full make test suite is green.

1 files changed, 95 insertions, 0 deletions

diff --git a/tests/test-ai-vterm--display-saved.el b/tests/test-ai-vterm--display-saved.el
new file mode 100644
index 00000000..9cb3521c
--- /dev/null
+++ b/tests/test-ai-vterm--display-saved.el
@@ -0,0 +1,95 @@
+;;; test-ai-vterm--display-saved.el --- Tests for the display-saved action -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; The action reads `cj/--ai-vterm-last-direction' +
+;; `cj/--ai-vterm-last-size' (with default fallbacks), builds an
+;; alist with direction + the matching size key, strips any
+;; conflicting entries that came in via the rule, and delegates to
+;; `display-buffer-in-direction'.
+;;
+;; Tests stub `display-buffer-in-direction' to capture the alist
+;; that would have reached it.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'ai-vterm)
+
+(ert-deftest test-ai-vterm--display-saved-uses-defaults-when-state-nil ()
+  "Normal: nil state -> direction=right, size=cj/ai-vterm-window-width."
+  (let (received-buf received-alist
+        (cj/--ai-vterm-last-direction nil)
+        (cj/--ai-vterm-last-size nil)
+        (cj/ai-vterm-window-width 0.5))
+    (cl-letf (((symbol-function 'display-buffer-in-direction)
+               (lambda (b a)
+                 (setq received-buf b received-alist a)
+                 'fake-window)))
+      (cj/--ai-vterm-display-saved 'fake-buf '((inhibit-same-window . t))))
+    (should (eq received-buf 'fake-buf))
+    (should (eq (cdr (assq 'direction received-alist)) 'right))
+    (should (= (cdr (assq 'window-width received-alist)) 0.5))
+    (should (eq (cdr (assq 'inhibit-same-window received-alist)) t))))
+
+(ert-deftest test-ai-vterm--display-saved-uses-saved-direction-and-size-below ()
+  "Normal: saved direction=below, size=0.4 -> below + window-height 0.4."
+  (let (received-alist
+        (cj/--ai-vterm-last-direction 'below)
+        (cj/--ai-vterm-last-size 0.4))
+    (cl-letf (((symbol-function 'display-buffer-in-direction)
+               (lambda (_b a) (setq received-alist a) 'fake-window)))
+      (cj/--ai-vterm-display-saved 'fake-buf nil))
+    (should (eq (cdr (assq 'direction received-alist)) 'below))
+    (should (= (cdr (assq 'window-height received-alist)) 0.4))
+    (should-not (assq 'window-width received-alist))))
+
+(ert-deftest test-ai-vterm--display-saved-uses-saved-direction-and-size-right ()
+  "Normal: saved direction=right, size=0.7 -> right + window-width 0.7."
+  (let (received-alist
+        (cj/--ai-vterm-last-direction 'right)
+        (cj/--ai-vterm-last-size 0.7))
+    (cl-letf (((symbol-function 'display-buffer-in-direction)
+               (lambda (_b a) (setq received-alist a) 'fake-window)))
+      (cj/--ai-vterm-display-saved 'fake-buf nil))
+    (should (eq (cdr (assq 'direction received-alist)) 'right))
+    (should (= (cdr (assq 'window-width received-alist)) 0.7))
+    (should-not (assq 'window-height received-alist))))
+
+(ert-deftest test-ai-vterm--display-saved-strips-conflicting-alist-entries ()
+  "Boundary: caller-supplied direction/size are stripped, saved values win."
+  (let (received-alist
+        (cj/--ai-vterm-last-direction 'right)
+        (cj/--ai-vterm-last-size 0.7))
+    (cl-letf (((symbol-function 'display-buffer-in-direction)
+               (lambda (_b a) (setq received-alist a) 'fake-window)))
+      (cj/--ai-vterm-display-saved
+       'fake-buf
+       '((direction . below)
+         (window-width . 0.2)
+         (window-height . 0.3)
+         (inhibit-same-window . t))))
+    (should (eq (cdr (assq 'direction received-alist)) 'right))
+    (should (= (cdr (assq 'window-width received-alist)) 0.7))
+    (should (eq (cdr (assq 'inhibit-same-window received-alist)) t))
+    ;; window-height should not be in the alist when direction is right
+    ;; -- the action picks the matching size key based on direction.
+    (let ((wh-cells (cl-remove-if-not
+                     (lambda (cell) (eq (car-safe cell) 'window-height))
+                     received-alist)))
+      (should (null wh-cells)))))
+
+(ert-deftest test-ai-vterm--display-saved-passes-buffer-through ()
+  "Normal: BUFFER argument reaches display-buffer-in-direction unchanged."
+  (let (received-buf
+        (cj/--ai-vterm-last-direction 'right)
+        (cj/--ai-vterm-last-size 0.5))
+    (cl-letf (((symbol-function 'display-buffer-in-direction)
+               (lambda (b _a) (setq received-buf b) 'fake-window)))
+      (cj/--ai-vterm-display-saved 'sentinel-buffer nil))
+    (should (eq received-buf 'sentinel-buffer))))
+
+(provide 'test-ai-vterm--display-saved)
+;;; test-ai-vterm--display-saved.el ends here