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>

libexec/devdesk-state-hook

@@ -16,7 +16,23 @@ outer=${TMUX:-}
 session=$(tmux display-message -p -t "$TMUX_PANE" '#S' 2>/dev/null)
 [[ $session =~ ^[A-Za-z0-9][A-Za-z0-9_-]{0,63}$ ]] || exit 0
 
-IFS=$'\t' read -r event message < <(jq -rM '[.hook_event_name // "", (.message // "" | gsub("[\t\n]"; " "))] | @tsv' <<<"$input" 2>/dev/null)
+# Unit separator, not tab: read collapses runs of whitespace delimiters, so an
+# empty field would shift the ones after it.
+IFS=$'\x1f' read -r event message tool file < <(jq -rM '[.hook_event_name // "", (.message // "" | gsub("[\u001f\n]"; " ")),
+    .tool_name // "", (.tool_input.file_path // .tool_input.notebook_path // "" | gsub("[\u001f\n]"; " "))] | join("\u001f")' <<<"$input" 2>/dev/null)
+
+# Files Claude edits, for the file viewer's "Claude" badge (devdesk#19).
+case $event:$tool in
+PostToolUse:Edit | PostToolUse:Write | PostToolUse:MultiEdit | PostToolUse:NotebookEdit)
+    if [[ $file == /* ]]; then
+        log="${DEVDESK_STATE_DIR:-/var/lib/devdesk}/edits/$session.txt"
+        mkdir -p "${log%/*}" 2>/dev/null
+        if ! grep -qxF -- "$file" "$log" 2>/dev/null && [ "$(wc -l <"$log" 2>/dev/null || echo 0)" -lt 1000 ]; then
+            printf '%s\n' "$file" >>"$log"
+        fi
+    fi
+    ;;
+esac
 case $event in
 UserPromptSubmit | PostToolUse) state=working ;;
 Notification) state=waiting ;;