feat: v0.11.0 VS Code-like explorer, markdown preview, search in files

- Explorer: context menus, multi-select, inline rename/new, drag to move
  or copy, desktop drag-and-drop uploads (folders too), cut/copy/paste,
  duplicate, download, delete to a 7-day trash with Undo. Server side in
  libexec/devdesk-fsops.sh with bats tests. Closes #54
- Markdown preview in a shadow root: headings with anchors and outline,
  highlighted code with copy, callouts, task lists, front matter, links
  that open files, live split view. Editor status bar, multi-cursor,
  closeBrackets, Ctrl+G, tab menus and reordering. Closes #55
- Search in files (Ctrl+Shift+F) via git grep / grep. Closes #56
- Fix: nested $(...) path checks now fail hard (set -e does not reach
  them; an escape created /x in testing); newest folder listing wins;
  sessionAction returns the reply JSON.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WHRLCCdXYm41Qx5kNhehaP

README.md

@@ -51,7 +51,15 @@ The tmux server runs in its own unit, so every Claude process lives in **that**
   - **`devdesk guests [ID|IP|NAME]`** lists Proxmox CTs/VMs with the node each runs on now, status, HA state and IPs. Claude is told to use it before acting, because HA guests move. Stopped guests keep the IP they had when last seen running.
   - Configure `DEVDESK_GRAFANA_URL`, plus a Viewer token in `DEVDESK_GRAFANA_TOKEN_FILE`. For the guest lookup, set `DEVDESK_PVE_NODES` to a few Proxmox nodes reachable by root SSH key. VM IPs need the QEMU guest agent.
 - **Repo / CI panel:** branch, ahead/behind, uncommitted changes, HEAD's Gitea CI status and open PRs for the session's folder. The first changed files are listed; click one for its diff against HEAD. When CI fails, **Ask Claude to fix CI** types a prompt to read the failed job's log.
-- **Files** (Ctrl+Shift+E), laid out like VS Code: an explorer tree (git colours, gitignored entries dimmed) and an editor with tabs (a click opens a preview tab, a double-click keeps it), **Go to file** (Ctrl+P in the pane), markdown previews (sanitized, with relative images), images, and a Changes view of uncommitted files with line counts, a **C** badge on files Claude edited, and diffs against HEAD. **@Claude** types `@path` into the prompt. Tabs and open folders are remembered per session. Paths can't leave the session folder.
+- **Files** (Ctrl+Shift+E), laid out like VS Code:
+  - **Explorer tree:** git colours, gitignored entries dimmed.
+  - **Mouse:** right-click menus (new file/folder, rename, delete, cut/copy/paste, duplicate, copy path, download, @Claude), Ctrl/Shift+click to select several, drag to move (Ctrl+drag copies). Drop files or whole folders from the desktop to upload them (up to 25 MB each), or drag a file onto the terminal to type `@path`.
+  - **Keyboard:** F2 renames in place, Delete trashes, Ctrl+C/X/V copy and paste files.
+  - **Safety:** delete goes to a 7-day trash with **Undo**; nothing is overwritten unless you choose Replace.
+  - **Editor:** tabs (a click opens a preview tab, a double-click keeps it; right-click for close variants; drag to reorder), **Go to file** (Ctrl+P in the pane), and **Search in files** (Ctrl+Shift+F: match case, whole word, regex). A status bar shows line/column, cursors, indentation, line endings and language. Multiple cursors (Alt+click), column select (Alt+drag), auto-closing brackets, Ctrl+G to go to a line.
+  - **Markdown preview:** GitHub-style headings with anchors and an outline, syntax-coloured code with Copy, callouts, task lists, front matter, images, and links that open files in DevDesk. **Split** shows the source and a live preview side by side.
+  - **Changes view:** uncommitted files with line counts, a **C** badge on files Claude edited, and diffs against HEAD. **@Claude** types `@path` into the prompt.
+  - **Remembered and contained:** tabs and open folders are remembered per session, and paths can't leave the session folder.
   - **Editing:** text files are editable; ● marks unsaved tabs; Ctrl+S (or Save) writes atomically and keeps the file's mode and owner. If the file changed on disk since you opened it (Claude edited it), saving asks: Compare (a diff of disk vs yours), Overwrite or Cancel; a change on disk while you edit shows a banner instead of replacing your text. Unsaved edits are kept as drafts in the browser, so a reload or a session switch doesn't lose them. ＋ creates a file (folders as needed). The editor bundle (`/usr/share/devdesk/assets/editor.js`) loads over ttyd the first time and is cached by the browser.
 - **Paths are links:** a file path Claude prints (`web/src/files.js`, `notes.md:12`) opens in Files when clicked, at that line if given.
 - **Ops guard:** `devdesk-guard` (a PreToolUse hook) makes Claude ask before destructive commands (`pct destroy`, `zfs destroy`, Ceph pool/OSD removal, `rm -r /…`, `git push --force`, `reboot`…), even in auto mode. `DEVDESK_GUARD=0` turns it off; `/etc/devdesk/guard.local` adds rules (`regex<TAB>reason`). Bash commands are logged per session, and sessions are tagged with the hosts they touch (ssh targets, CT/VM ids).
@@ -73,6 +81,8 @@ The tmux server runs in its own unit, so every Claude process lives in **that**
 | Ctrl-b d | Detach (the session keeps running) |
 | Drag | Selects text; it stays highlighted and is copied when you let go. Double-click selects a word, triple-click a line. Clicks on the tmux status line still go to tmux. |
 | Ctrl+C | Copies the selection when there is one; otherwise interrupts as usual |
+| Ctrl+Shift+F | Search in the session's files |
+| F2 / Delete / Ctrl+C·X·V (explorer) | Rename, move to trash, copy/cut/paste files |
 | Palette → Close split panes | Removes extra tmux panes (a stray `^b %` split) and keeps Claude. tmux's right-click menus are off. |
 | Ctrl+Shift+C / V | Copy selection / paste |
 | Ctrl+Shift+P | Command palette (also the ⌕ button) |