* gui: dock Changes as a right-hand panel beside the terminals

The modal Working Tree Changes dialog becomes a persistent panel in an end-side AdwOverlaySplitView (Ctrl+Shift+D): files grouped by directory with +N/-N in the diff colours, the existing reader pushed inside it, and the panel following the active workspace. Breakpoints are reordered because only the last matching one applies.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* docs: specify the docked Changes panel

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* gui: keep the Changes panel from re-reading git on agent events

Model refreshes re-show the active workspace on every agent event; the panel now only follows a workspace switch and reads on open or Refresh.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* gui: group Changes by directory, describe rows, focus the visible page

Review fixes: sort by (directory, name) so a subdirectory cannot split its parent's group, expose the full path as each row's accessible description, and focus the reader when the panel reopens on it. A test pins the native focus hand-back to the terminal on close.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* docs: drop the stale dialog-closure wording for the Changes reader

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>