feat(ai-term): add s-F9 step-to-next-agent, drop C-S-F9 close alias

s-F9 (cj/ai-term-next) steps through the open agent buffers in name order. It's the "switch among existing agents" surface F9's toggle never provided. The cycle logic lives in a pure helper (cj/--ai-term-next-agent-buffer) with Normal/Boundary/Error coverage. The command is a thin window-mutating wrapper.

I dropped the C-S-F9 close alias, leaving M-F9 as the sole close binding. I moved cj/server-shutdown off C-<f10> to C-x C so the key keeps forwarding to the terminal program inside an agent buffer. I also removed the now-unused F10 entries from term-config's ghostel exceptions.

2 files changed, 83 insertions, 8 deletions

diff --git a/tests/test-ai-term--f9-in-term.el b/tests/test-ai-term--f9-in-term.el
index dad11ffc0..0477f2517 100644
--- a/tests/test-ai-term--f9-in-term.el
+++ b/tests/test-ai-term--f9-in-term.el
@@ -26,27 +26,29 @@
   (should (eq (keymap-lookup ghostel-mode-map "<f9>") #'cj/ai-term)))
 
 (ert-deftest test-ai-term-f9-family-bound-in-ghostel-mode-map ()
-  "Normal: the C-/M-/C-S- F9 variants are bound in `ghostel-mode-map' too.
-`M-<f9>' and `C-S-<f9>' both close an agent via `cj/ai-term-close'."
+  "Normal: the C-/s-/M- F9 variants are bound in `ghostel-mode-map' too.
+`s-<f9>' steps to the next agent; `M-<f9>' closes an agent via
+`cj/ai-term-close'."
   (should (eq (keymap-lookup ghostel-mode-map "C-<f9>") #'cj/ai-term-pick-project))
-  (should (eq (keymap-lookup ghostel-mode-map "M-<f9>") #'cj/ai-term-close))
-  (should (eq (keymap-lookup ghostel-mode-map "C-S-<f9>") #'cj/ai-term-close)))
+  (should (eq (keymap-lookup ghostel-mode-map "s-<f9>") #'cj/ai-term-next))
+  (should (eq (keymap-lookup ghostel-mode-map "M-<f9>") #'cj/ai-term-close)))
 
 (ert-deftest test-ai-term-f9-still-bound-globally ()
   "Normal: the global F9 family bindings are intact.
 `<f9>' toggles the ai-term agent window; `C-<f9>' picks a project
-agent; `M-<f9>' and `C-S-<f9>' close an agent via `cj/ai-term-close'."
+agent; `s-<f9>' steps to the next agent; `M-<f9>' closes an agent
+via `cj/ai-term-close'."
   (should (eq (lookup-key (current-global-map) (kbd "<f9>")) #'cj/ai-term))
   (should (eq (lookup-key (current-global-map) (kbd "C-<f9>")) #'cj/ai-term-pick-project))
-  (should (eq (lookup-key (current-global-map) (kbd "M-<f9>")) #'cj/ai-term-close))
-  (should (eq (lookup-key (current-global-map) (kbd "C-S-<f9>")) #'cj/ai-term-close)))
+  (should (eq (lookup-key (current-global-map) (kbd "s-<f9>")) #'cj/ai-term-next))
+  (should (eq (lookup-key (current-global-map) (kbd "M-<f9>")) #'cj/ai-term-close)))
 
 (ert-deftest test-ai-term-f9-family-in-keymap-exceptions ()
   "Regression: the F9 family is in `ghostel-keymap-exceptions' so semi-char
 mode lets it reach Emacs instead of forwarding it to the terminal program.
 Binding in `ghostel-mode-map' alone is not enough -- the semi-char map outranks
 it and forwards any key not in the exceptions to the pty."
-  (dolist (key '("<f9>" "C-<f9>" "M-<f9>" "C-S-<f9>"))
+  (dolist (key '("<f9>" "C-<f9>" "s-<f9>" "M-<f9>"))
     (should (member key ghostel-keymap-exceptions)))
   ;; The rebuilt semi-char map must no longer forward <f9> to the pty.
   (should-not (eq (keymap-lookup ghostel-semi-char-mode-map "<f9>")
diff --git a/tests/test-ai-term--next-agent-buffer.el b/tests/test-ai-term--next-agent-buffer.el
new file mode 100644
index 000000000..330714a92
--- /dev/null
+++ b/tests/test-ai-term--next-agent-buffer.el
@@ -0,0 +1,73 @@
+;;; test-ai-term--next-agent-buffer.el --- Tests for cj/--ai-term-next-agent-buffer -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; The pure decision helper behind `cj/ai-term-next' (s-F9).  Given the
+;; current agent buffer and the ordered list of live agent buffers, it
+;; returns the next buffer in the queue, wrapping after the last.  A nil
+;; or non-member CURRENT returns the first; an empty list returns nil.
+;; No buffer or window side effects -- list logic only.
+
+;;; Code:
+
+(require 'ert)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'ai-term)
+
+(ert-deftest test-ai-term--next-agent-buffer-advances-from-first ()
+  "Normal: current is the first element -> returns the second."
+  (let ((a (get-buffer-create "agent [a]"))
+        (b (get-buffer-create "agent [b]"))
+        (c (get-buffer-create "agent [c]")))
+    (unwind-protect
+        (should (eq b (cj/--ai-term-next-agent-buffer a (list a b c))))
+      (mapc #'kill-buffer (list a b c)))))
+
+(ert-deftest test-ai-term--next-agent-buffer-advances-from-middle ()
+  "Normal: current in the middle -> returns the following element."
+  (let ((a (get-buffer-create "agent [a]"))
+        (b (get-buffer-create "agent [b]"))
+        (c (get-buffer-create "agent [c]")))
+    (unwind-protect
+        (should (eq c (cj/--ai-term-next-agent-buffer b (list a b c))))
+      (mapc #'kill-buffer (list a b c)))))
+
+(ert-deftest test-ai-term--next-agent-buffer-wraps-after-last ()
+  "Boundary: current is the last element -> wraps to the first."
+  (let ((a (get-buffer-create "agent [a]"))
+        (b (get-buffer-create "agent [b]"))
+        (c (get-buffer-create "agent [c]")))
+    (unwind-protect
+        (should (eq a (cj/--ai-term-next-agent-buffer c (list a b c))))
+      (mapc #'kill-buffer (list a b c)))))
+
+(ert-deftest test-ai-term--next-agent-buffer-single-element-returns-itself ()
+  "Boundary: a one-agent queue wraps current back to itself."
+  (let ((a (get-buffer-create "agent [a]")))
+    (unwind-protect
+        (should (eq a (cj/--ai-term-next-agent-buffer a (list a))))
+      (kill-buffer a))))
+
+(ert-deftest test-ai-term--next-agent-buffer-nil-current-returns-first ()
+  "Boundary: nil current (no agent displayed) -> returns the first."
+  (let ((a (get-buffer-create "agent [a]"))
+        (b (get-buffer-create "agent [b]")))
+    (unwind-protect
+        (should (eq a (cj/--ai-term-next-agent-buffer nil (list a b))))
+      (mapc #'kill-buffer (list a b)))))
+
+(ert-deftest test-ai-term--next-agent-buffer-non-member-current-returns-first ()
+  "Error: current not in the queue -> returns the first rather than nil."
+  (let ((a (get-buffer-create "agent [a]"))
+        (b (get-buffer-create "agent [b]"))
+        (stray (get-buffer-create "agent [stray]")))
+    (unwind-protect
+        (should (eq a (cj/--ai-term-next-agent-buffer stray (list a b))))
+      (mapc #'kill-buffer (list a b stray)))))
+
+(ert-deftest test-ai-term--next-agent-buffer-empty-queue-returns-nil ()
+  "Boundary: an empty queue returns nil (nothing to switch to)."
+  (should (null (cj/--ai-term-next-agent-buffer nil '()))))
+
+(provide 'test-ai-term--next-agent-buffer)
+;;; test-ai-term--next-agent-buffer.el ends here