feat(signal): dock chat buffer to bottom 30% and add cancel binding

I added a display-buffer-alist entry matching "*Signel:" chat buffers and routing them through display-buffer-at-bottom with window-height 0.3. The signel fork's signel-chat now uses pop-to-buffer instead of switch-to-buffer, which is what makes the rule apply. Without that switch the buffer replaces the current window and skips display-buffer entirely.

Two new tests in test-signal-config.el lock the entry shape and the regex's buffer-name match set. A new test-signel-cancel-input.el covers the fork's C-c C-k handler. It clears the editable region between signel--input-marker and point-max, then quit-windows so the buffer survives the dismiss.

Closes the "Chat buffer placement + exit keys" task filed during the 2026-05-28 manual-verify walk.

2 files changed, 99 insertions, 0 deletions

diff --git a/tests/test-signal-config.el b/tests/test-signal-config.el
index b362e03b..3be63362 100644
--- a/tests/test-signal-config.el
+++ b/tests/test-signal-config.el
@@ -368,5 +368,30 @@ commands the workflow spec names."
   (should (eq (keymap-lookup cj/signel-prefix-map "SPC")
               #'cj/signel-connect)))
 
+;;; display-buffer-alist entry for *Signel: ...* chat buffers
+
+(ert-deftest test-signal-config-chat-buffer-display-rule-uses-bottom-30 ()
+  "Normal: signal-config registers a `display-buffer-alist' entry that
+matches `*Signel: <id>*' buffers, routes them through
+`display-buffer-at-bottom', and sets `window-height' to 0.3 so the
+chat docks to the bottom 30% of the frame."
+  (let ((entry (seq-find (lambda (e) (equal (car e) "\\`\\*Signel: "))
+                         display-buffer-alist)))
+    (should entry)
+    (should (memq 'display-buffer-at-bottom (cadr entry)))
+    (should (equal 0.3 (cdr (assq 'window-height (cddr entry)))))))
+
+(ert-deftest test-signal-config-chat-buffer-display-rule-matches-buffer-name ()
+  "Boundary: the registered regex matches a realistic chat buffer name
+\(phone-number id and group-id) and does not match unrelated buffers."
+  (let* ((entry (seq-find (lambda (e) (equal (car e) "\\`\\*Signel: "))
+                          display-buffer-alist))
+         (regex (car entry)))
+    (should regex)
+    (should (string-match-p regex "*Signel: +15555550100*"))
+    (should (string-match-p regex "*Signel: groupid-abc*"))
+    (should-not (string-match-p regex "*signel-log*"))
+    (should-not (string-match-p regex "scratch"))))
+
 (provide 'test-signal-config)
 ;;; test-signal-config.el ends here
diff --git a/tests/test-signel-cancel-input.el b/tests/test-signel-cancel-input.el
new file mode 100644
index 00000000..b2a7ef89
--- /dev/null
+++ b/tests/test-signel-cancel-input.el
@@ -0,0 +1,74 @@
+;;; test-signel-cancel-input.el --- Cancel-input contract for the signel fork -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; `signel--cancel-input' is the C-c C-k handler in `signel-chat-mode'.
+;; Its contract: clear any in-progress input between `signel--input-marker'
+;; and `point-max' (so the prompt is fresh on next visit), then dismiss
+;; the window via `quit-window' (the buffer stays alive so chat history
+;; survives revisits).  These tests lock the contract; the binding test
+;; locks the keymap entry.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+
+(eval-and-compile
+  (add-to-list 'load-path (expand-file-name "~/code/signel")))
+(require 'signel)
+
+(defmacro test-signel-cancel--with-chat-buffer (&rest body)
+  "Set up a temp signel-chat-mode buffer with prompt drawn and run BODY."
+  (declare (indent 0))
+  `(with-temp-buffer
+     (signel-chat-mode)
+     (setq signel--chat-id "+15555550100")
+     (signel--draw-prompt)
+     ,@body))
+
+(ert-deftest test-signel-cancel-input-clears-pending-text ()
+  "Normal: pending input from input-marker to point-max is cleared."
+  (test-signel-cancel--with-chat-buffer
+    (insert "abandoned-draft")
+    (cl-letf (((symbol-function 'quit-window) (lambda (&rest _) nil)))
+      (signel--cancel-input))
+    (should-not (signel--pending-input))))
+
+(ert-deftest test-signel-cancel-input-empty-input-area-is-a-noop ()
+  "Boundary: cancelling with no in-progress input is harmless."
+  (test-signel-cancel--with-chat-buffer
+    (cl-letf (((symbol-function 'quit-window) (lambda (&rest _) nil)))
+      (signel--cancel-input))
+    (should-not (signel--pending-input))))
+
+(ert-deftest test-signel-cancel-input-calls-quit-window ()
+  "Normal: cancel dismisses the window via `quit-window'."
+  (test-signel-cancel--with-chat-buffer
+    (insert "abandoned-draft")
+    (let ((called nil))
+      (cl-letf (((symbol-function 'quit-window)
+                 (lambda (&rest _) (setq called t))))
+        (signel--cancel-input))
+      (should called))))
+
+(ert-deftest test-signel-cancel-input-preserves-buffer ()
+  "Normal: cancel does not kill the buffer; chat history (prompt + prior
+content above the input marker) survives so reopening the contact lands
+in the same buffer."
+  (test-signel-cancel--with-chat-buffer
+    (insert "abandoned-draft")
+    (let ((buf (current-buffer)))
+      (cl-letf (((symbol-function 'quit-window) (lambda (&rest _) nil)))
+        (signel--cancel-input))
+      (should (buffer-live-p buf)))))
+
+(ert-deftest test-signel-chat-mode-binds-c-c-c-k-to-cancel ()
+  "Normal: `signel-chat-mode' binds C-c C-k to `signel--cancel-input' so
+the documented cancel gesture reaches the handler."
+  (with-temp-buffer
+    (signel-chat-mode)
+    (should (eq (lookup-key (current-local-map) (kbd "C-c C-k"))
+                #'signel--cancel-input))))
+
+(provide 'test-signel-cancel-input)
+;;; test-signel-cancel-input.el ends here