feat: v0.9.2 Ask Claude on an alert starts an investigation session

- Ops Alerts → Ask Claude now calls `devdesk attach --investigate SESSION UID`.
  The server looks the alert up, writes the prompt and starts Claude in a new
  alert-<name> session with it as the first prompt, already sent. Prompts are
  stored in prompts/<session>.txt and consumed once by devdesk-claude-run.
  A session that is already running is just opened.
- The prompt has the rule, query, summary, details and labels, and where it
  runs: the CT/VM id, the node it is on now, status and HA state, and
  `ssh <node> pct exec <id> --`. It reminds Claude that HA guests move
  (`devdesk guests <id>`), and gives aggregate rules a hint.
- `devdesk guests`: Proxmox inventory over SSH (DEVDESK_PVE_NODES). pvesh
  gives the cluster view; each node gives lxc-info and guest-agent IPs.
  Cached in guests.json, keeping last-seen IPs for stopped guests; --alerts
  refreshes it in the background every 5 minutes.
- Alerts carry uid, query, description and targets, matched by instance
  IP/host or by name; each card shows the target.
- cmd_alerts moves to libexec/devdesk-ops.sh.

Closes #39

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

README.md

@@ -43,9 +43,11 @@ The tmux server runs in its own unit, so every Claude process lives in **that**
 - **File & image drop:** drag files onto the terminal or paste a screenshot.
   - They're uploaded through ttyd to `/var/lib/devdesk/uploads/<session>/` (25 MB max, pruned after 7 days), and the path is pasted into Claude.
   - For images, Claude attaches them itself.
-- **Ops Alerts panel:** firing and pending Grafana alert rules, each with a link to the rule.
-  - **Ask Claude** types an investigation prompt into the current session without sending it.
-  - Configure `DEVDESK_GRAFANA_URL`, plus a Viewer token in `DEVDESK_GRAFANA_TOKEN_FILE`.
+- **Ops Alerts panel:** firing and pending Grafana alert rules, each with a link to the rule and the Proxmox guest or node it's about, e.g. `→ CT 110 draupnir · monitor-02 · stopped`.
+  - **Ask Claude** starts Claude in a new session (`alert-<name>`) with the investigation already sent. The prompt has the rule, its query, summary and labels, and where it runs: the CT/VM id, the node it's on right now, and the `ssh <node> pct exec <id> --` line. Clicking it again just opens that session.
+  - Guests are matched by the alert's `instance` IP (or host name), else by name in the job or alert ("by name"). Aggregate rules with no labels (`count(up == 0)`) get a hint to run the inner query instead.
+  - **`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. 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.
   - **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.