fix(ai-vterm): direction-based display + per-project tmux session names

Two post-ship issues blocked practical use of the new launcher.

The display rule used `display-buffer-in-side-window` with `(dedicated . t)`. Side-window dedication caused `set-window-buffer` to error during `buffer-move` (C-M-arrows), which left a half-finished swap with both sides showing the claude buffer. Then `switch-to-buffer` on a non-claude buffer in that dedicated window split instead of replacing.

I rewrote the rule as `display-buffer-reuse-window -> display-buffer-use-some-window -> display-buffer-in-direction (right)`. The resulting window is ordinary, not dedicated, so swap and replace work normally. I also narrowed `vterm-toggle`'s broad lambda (which matches any vterm-mode buffer) to exclude `claude [` buffers. Otherwise vterm-toggle's `:defer` made it install last and capture our buffers first with its own bottom-split + dedicated treatment.

The tmux side: vterm's auto-launch hook ran a bare `tmux\n`, so each session got an auto-named one. After an Emacs crash the tmux session would survive but I couldn't find it. A second F9 just spawned another. The launcher now sends `tmux new-session -A -s <basename> -c <dir> '<claude>; exec bash'`. The `-A` reattaches to a same-named session if it already exists. The `exec bash` keeps the tmux window alive if claude itself exits. A `cj/--ai-vterm-suppress-tmux` flag tells the existing vterm hook to skip its bare tmux step so the named launch runs instead.

11 new tests across 2 files cover the session-name and launch-command helpers. I updated tests for show-or-create and the display rule. All 34 ai-vterm tests are green.

3 files changed, 109 insertions, 3 deletions

diff --git a/tests/test-ai-vterm--launch-command.el b/tests/test-ai-vterm--launch-command.el
new file mode 100644
index 00000000..c6b7ac2b
--- /dev/null
+++ b/tests/test-ai-vterm--launch-command.el
@@ -0,0 +1,61 @@
+;;; test-ai-vterm--launch-command.el --- Tests for cj/--ai-vterm-launch-command -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; The launch command is what gets typed into a fresh vterm shell to bring
+;; up Claude inside a per-project tmux session.  The session is named after
+;; the project basename so a second F9 on the same project reattaches to
+;; the running Claude rather than spawning a new one.  The trailing
+;; `exec bash' keeps the tmux window alive if Claude exits, leaving the
+;; session intact for recovery.
+
+;;; Code:
+
+(require 'ert)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'ai-vterm)
+
+(ert-deftest test-ai-vterm--launch-command-uses-new-session-attach ()
+  "Normal: starts with `tmux new-session -A' so existing sessions reattach."
+  (let ((cj/ai-vterm-claude-command "claude"))
+    (should (string-prefix-p
+             "tmux new-session -A "
+             (cj/--ai-vterm-launch-command "/code/foo")))))
+
+(ert-deftest test-ai-vterm--launch-command-includes-session-name ()
+  "Normal: the session name comes from the basename helper."
+  (let ((cj/ai-vterm-claude-command "claude"))
+    (should (string-match-p
+             " -s foo "
+             (cj/--ai-vterm-launch-command "/code/foo")))))
+
+(ert-deftest test-ai-vterm--launch-command-includes-start-directory ()
+  "Normal: `-c <dir>' so the new session's first window starts in DIR."
+  (let ((cj/ai-vterm-claude-command "claude"))
+    (should (string-match-p
+             " -c /code/foo "
+             (cj/--ai-vterm-launch-command "/code/foo")))))
+
+(ert-deftest test-ai-vterm--launch-command-includes-claude-command ()
+  "Normal: the configured claude command is in the launched shell command."
+  (let ((cj/ai-vterm-claude-command "claude --some-flag"))
+    (should (string-match-p
+             "claude --some-flag"
+             (cj/--ai-vterm-launch-command "/code/foo")))))
+
+(ert-deftest test-ai-vterm--launch-command-tails-with-exec-bash ()
+  "Boundary: `exec bash' tails so the tmux window survives Claude exiting."
+  (let ((cj/ai-vterm-claude-command "claude"))
+    (should (string-match-p
+             "exec bash"
+             (cj/--ai-vterm-launch-command "/code/foo")))))
+
+(ert-deftest test-ai-vterm--launch-command-handles-spaces-in-basename ()
+  "Boundary: a basename with whitespace becomes hyphenated before quoting."
+  (let ((cj/ai-vterm-claude-command "claude"))
+    (should (string-match-p
+             " -s my-work "
+             (cj/--ai-vterm-launch-command "/code/my work")))))
+
+(provide 'test-ai-vterm--launch-command)
+;;; test-ai-vterm--launch-command.el ends here
diff --git a/tests/test-ai-vterm--show-or-create.el b/tests/test-ai-vterm--show-or-create.el
index 28e0faeb..3faf5f03 100644
--- a/tests/test-ai-vterm--show-or-create.el
+++ b/tests/test-ai-vterm--show-or-create.el
@@ -57,7 +57,7 @@ VARS is a plist of capture variable names: :calls, :strings, :returns,
     (kill-buffer name)))
 
 (ert-deftest test-ai-vterm--show-or-create-creates-when-buffer-missing ()
-  "Normal: no existing buffer -> vterm called once, claude cmd sent."
+  "Normal: no existing buffer -> vterm called once, launch cmd sent."
   (let ((name "claude [normal-create-test]"))
     (test-ai-vterm--cleanup name)
     (unwind-protect
@@ -65,7 +65,8 @@ VARS is a plist of capture variable names: :calls, :strings, :returns,
                                          :returns returns :default-dir ddir)
           (cj/--ai-vterm-show-or-create "/tmp/some-project" name)
           (should (equal calls (list name)))
-          (should (equal strings (list cj/ai-vterm-claude-command)))
+          (should (equal strings
+                         (list (cj/--ai-vterm-launch-command "/tmp/some-project"))))
           (should (= returns 1))
           (should (equal ddir "/tmp/some-project")))
       (test-ai-vterm--cleanup name))))
@@ -98,7 +99,8 @@ VARS is a plist of capture variable names: :calls, :strings, :returns,
                                              :returns returns :default-dir _ddir)
               (cj/--ai-vterm-show-or-create "/tmp/dead" name)
               (should (equal calls (list name)))
-              (should (equal strings (list cj/ai-vterm-claude-command)))
+              (should (equal strings
+                             (list (cj/--ai-vterm-launch-command "/tmp/dead"))))
               (should (= returns 1))
               (should-not (buffer-live-p stale)))))
       (test-ai-vterm--cleanup name))))
diff --git a/tests/test-ai-vterm--tmux-session-name.el b/tests/test-ai-vterm--tmux-session-name.el
new file mode 100644
index 00000000..9d56040e
--- /dev/null
+++ b/tests/test-ai-vterm--tmux-session-name.el
@@ -0,0 +1,43 @@
+;;; test-ai-vterm--tmux-session-name.el --- Tests for cj/--ai-vterm-tmux-session-name -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; The tmux session name is derived from the project's basename so that
+;; reopening Claude on the same project (e.g. after an Emacs crash)
+;; reattaches to the same tmux session rather than spawning a new one.
+;; Whitespace in the basename gets converted to hyphens so the name is
+;; safe to pass on a tmux command line.
+
+;;; Code:
+
+(require 'ert)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'ai-vterm)
+
+(ert-deftest test-ai-vterm--tmux-session-name-normal-project ()
+  "Normal: a typical project path yields its basename."
+  (should (equal (cj/--ai-vterm-tmux-session-name "/home/cjennings/projects/foo")
+                 "foo")))
+
+(ert-deftest test-ai-vterm--tmux-session-name-trailing-slash ()
+  "Boundary: trailing slash collapses before basename extraction."
+  (should (equal (cj/--ai-vterm-tmux-session-name "/home/cjennings/projects/foo/")
+                 "foo")))
+
+(ert-deftest test-ai-vterm--tmux-session-name-dot-prefix-dir ()
+  "Boundary: dot-prefix dirs preserve the dot (tmux accepts dots)."
+  (should (equal (cj/--ai-vterm-tmux-session-name "/home/cjennings/.emacs.d")
+                 ".emacs.d")))
+
+(ert-deftest test-ai-vterm--tmux-session-name-space-becomes-hyphen ()
+  "Boundary: a space in the basename is replaced with a hyphen."
+  (should (equal (cj/--ai-vterm-tmux-session-name "/tmp/my work")
+                 "my-work")))
+
+(ert-deftest test-ai-vterm--tmux-session-name-multiple-spaces-collapse ()
+  "Boundary: a run of whitespace collapses to a single hyphen."
+  (should (equal (cj/--ai-vterm-tmux-session-name "/tmp/a   b\tc")
+                 "a-b-c")))
+
+(provide 'test-ai-vterm--tmux-session-name)
+;;; test-ai-vterm--tmux-session-name.el ends here