fix(keybindings): retire the two-column F2 and C-x 6 bindings

A grazed F2 followed by a stray 2, s, or b invokes two-column mode, which replaces the buffer's mode-line-format with its own retro layout and spawns a 2C/ companion buffer. That's what mangled the modeline in an agent terminal: eat semi-char buffers don't forward F2, so the prefix was armed everywhere. Nothing of mine uses global F2 (markdown-mode's binding lives in its own map), so I unbound both routes to 2C-command. cj/modeline-reset repairs a hijacked buffer.

1 files changed, 26 insertions, 0 deletions

diff --git a/tests/test-keybindings-two-column-unbound.el b/tests/test-keybindings-two-column-unbound.el
new file mode 100644
index 00000000..f9bc2c52
--- /dev/null
+++ b/tests/test-keybindings-two-column-unbound.el
@@ -0,0 +1,26 @@
+;;; test-keybindings-two-column-unbound.el --- 2C-command is unbound -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Two-column mode's global F2 / C-x 6 prefix replaces a buffer's
+;; mode-line-format with its own layout when triggered by a stray
+;; keypress (the 2026-07-01 archsetup agent-buffer incident).
+;; keybindings.el retires both bindings; these tests pin that.
+
+;;; Code:
+
+(require 'ert)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+
+(require 'keybindings)
+
+(ert-deftest test-keybindings-two-column-f2-unbound ()
+  "Normal: F2 no longer reaches the 2C-command prefix."
+  (should-not (keymap-lookup global-map "<f2>")))
+
+(ert-deftest test-keybindings-two-column-c-x-6-unbound ()
+  "Normal: C-x 6 no longer reaches the 2C-command prefix."
+  (should-not (keymap-lookup global-map "C-x 6")))
+
+(provide 'test-keybindings-two-column-unbound)
+;;; test-keybindings-two-column-unbound.el ends here