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.

1 files changed, 25 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