feat(windows): dock companion panels by a shared min-column rule

The F9 agent always docked as a right-side column on a landscape frame. On this 138-column frame that left ~68-column panes, too cramped to read code and the agent side by side. The F12 terminal and F10 playlist hardcoded a bottom split with no width-aware path.

I added cj/preferred-dock-direction and the cj/window-dock-min-columns defcustom (default 80) to the window-geometry lib: dock side-by-side only when the narrower pane keeps at least the minimum width, otherwise stack below. All three toggles now route through it. F9 drops its pixel-aspect rule. F12 and F10 gain a right-column width default and become adaptive. F10 keeps width and height size memory in separate vars so a resize on one axis doesn't leak to the other.

1 files changed, 45 insertions, 0 deletions

diff --git a/tests/test-music-config--playlist-side.el b/tests/test-music-config--playlist-side.el
new file mode 100644
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+++ b/tests/test-music-config--playlist-side.el
@@ -0,0 +1,45 @@
+;;; test-music-config--playlist-side.el --- Tests for the F10 dock-side helper -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; `cj/--music-playlist-side' maps the shared dock rule's verdict to a
+;; `display-buffer-in-side-window' side: `right' stays `right', anything
+;; else becomes `bottom'.  The decision itself lives in
+;; `cj/preferred-dock-direction' (tested in test-cj-window-geometry-lib.el);
+;; here we stub it (an ordinary defun -- safe to `cl-letf', unlike the
+;; frame-* subrs) to prove the mapping and that the width fraction is
+;; passed through.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'music-config)
+
+(ert-deftest test-music-config--playlist-side-right-verdict-is-right ()
+  "Normal: a `right' verdict from the dock rule docks the playlist right."
+  (cl-letf (((symbol-function 'cj/preferred-dock-direction)
+             (lambda (&rest _) 'right)))
+    (should (eq (cj/--music-playlist-side) 'right))))
+
+(ert-deftest test-music-config--playlist-side-below-verdict-is-bottom ()
+  "Normal: a `below' verdict maps to the `bottom' side window."
+  (cl-letf (((symbol-function 'cj/preferred-dock-direction)
+             (lambda (&rest _) 'below)))
+    (should (eq (cj/--music-playlist-side) 'bottom))))
+
+(ert-deftest test-music-config--playlist-side-passes-width-fraction ()
+  "Normal: the playlist's width fraction reaches the dock rule."
+  (let ((cj/music-playlist-window-width 0.4)
+        captured)
+    (cl-letf (((symbol-function 'cj/preferred-dock-direction)
+               (lambda (cols frac &rest _)
+                 (setq captured (list cols frac))
+                 'below)))
+      (cj/--music-playlist-side)
+      (should (= (nth 1 captured) 0.4))
+      (should (integerp (nth 0 captured))))))
+
+(provide 'test-music-config--playlist-side)
+;;; test-music-config--playlist-side.el ends here