feat: v0.7.0 files pane: browse, preview, diff, Claude's edits

- devdesk attach --fs-list/--fs-read/--git-status/--git-show/--asset
  (libexec/devdesk-files.sh), confined to the session folder.
- The state hook records files Claude edits (Edit/Write/MultiEdit/
  NotebookEdit) for the Changes tab's "C" badge; rename/end carry it.
- Files pane: folders, CodeMirror read-only view, sanitized markdown preview
  in a sandboxed iframe with inlined relative images, images, Changes tab with
  line counts and diff against HEAD, "→ Claude" @path, resizable split.
- The editor bundle ships as /usr/share/devdesk/assets/editor.js, is fetched
  over ttyd on first use, verified against the page's SHA-256 and cached in
  IndexedDB.
- Fix: the state hook's field split collapsed empty fields.

Closes #19

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

debian/changelog

@@ -1,3 +1,27 @@
+devdesk (0.7.0) bookworm; urgency=medium
+
+  * Files pane (#19): a Files button (Ctrl+Shift+E) next to Panels opens the
+    session's folder beside the terminal (a drag-resizable split on wide
+    screens, an overlay on narrow ones and phones).
+    - Browse folders; read files with syntax highlighting (CodeMirror,
+      read-only, Ctrl+F search, line wrap toggle), markdown rendered as a
+      sanitized preview with its relative images, images shown inline.
+    - Changes tab: uncommitted git changes with line counts and a "C" badge
+      on files Claude edited (recorded by the state hook from Edit/Write);
+      diff against HEAD for any changed file. Non-git sessions list the files
+      Claude edited there.
+    - "→ Claude" types @path into the prompt; Copy path.
+    - After Claude's turn the list refreshes, and an open file that changed
+      on disk offers a reload.
+    - Paths stay inside the session folder (no absolute paths, no symlink
+      escapes). Read-only for now; editing is v0.8.0.
+    - The editor (~600 KB) is not in the page: it ships in
+      /usr/share/devdesk/assets, is fetched over ttyd the first time Files
+      opens, checked against the page's SHA-256 and cached in the browser.
+  * Fix: the state hook mis-read hook fields when Claude's message was empty.
+
+ -- Jared Vititoe <jjvititoe1@gmail.com>  Thu, 08 Oct 2026 01:16:26 -0400
+
 devdesk (0.6.1) bookworm; urgency=medium
 
   * Inbox bell (#36): sessions waiting on you, firing alerts, and what