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>

package.json

@@ -4,21 +4,34 @@
   "description": "Persistent browser terminal for Claude Code (ttyd + tmux), LotusGuild TDS styling",
   "license": "MIT",
   "type": "module",
-  "engines": { "node": ">=18" },
+  "engines": {
+    "node": ">=18"
+  },
   "scripts": {
     "build": "node web/build.mjs",
-    "lint": "eslint --ext .js,.mjs web/src web/build.mjs tests/protocol.test.mjs",
+    "lint": "eslint --ext .js,.mjs web/src web/editor web/build.mjs tests/protocol.test.mjs",
     "test": "node --test tests/*.test.mjs"
   },
   "devDependencies": {
+    "@codemirror/commands": "6.11.1",
+    "@codemirror/lang-markdown": "6.5.2",
+    "@codemirror/language": "6.13.1",
+    "@codemirror/legacy-modes": "6.5.5",
+    "@codemirror/merge": "6.12.2",
+    "@codemirror/search": "6.7.2",
+    "@codemirror/state": "6.7.6",
+    "@codemirror/view": "6.43.14",
     "@fontsource/jetbrains-mono": "5.3.0",
+    "@lezer/highlight": "1.2.5",
     "@xterm/addon-clipboard": "0.2.0",
     "@xterm/addon-fit": "0.11.0",
     "@xterm/addon-unicode11": "0.9.0",
     "@xterm/addon-web-links": "0.12.0",
     "@xterm/addon-webgl": "0.19.0",
     "@xterm/xterm": "6.0.0",
+    "dompurify": "3.4.16",
     "esbuild": "0.28.2",
-    "eslint": "8.57.1"
+    "eslint": "8.57.1",
+    "marked": "18.1.0"
   }
 }