refactor!: rebrand CCAM to AgentHub

Clean break, no compatibility alias. Renames the product name, the CLI
binary (`ccam` -> `agenthub`), the env var prefix (`CCAM_` ->
`AGENTHUB_`), the Prometheus metric namespace (`ccam_*` ->
`agenthub_*`), the tmux session prefix (`ccam-lane-<id>` ->
`agenthub-lane-<id>`), the per-repo runtime profile directory
(`.ccam/profile` -> `.agenthub/profile`), the lanes state root
(`~/.claude/ccam-lanes` -> `~/.claude/agenthub-lanes`), the bundled
plugins (`plugins/ccam*` -> `plugins/agenthub*`) and their slash
commands (`/ccam-doctor` -> `/agenthub-doctor`, `/ccam:*` ->
`/agenthub:*`).

Because there is no alias, an existing install has to be updated by
hand: rename its `.ccam/profile` directory and any `CCAM_*` variables,
and reinstall the plugin under its new name.

Two other name families are deliberately left alone here, since they are
not just strings: the `Claude-Code-Monitor` repository/marketplace name,
and the `agent-dashboard` npm package plus its `~/.claude/agent-dashboard`
runtime directory, which holds the live database and needs a migration
rather than a rename.

Verified: server 1406/1406, client 459/459, `grep -i ccam` clean across
tracked files, `openapi.yaml` regenerated (95 paths, unchanged count).

plugins/agenthub-dashboard/commands/status.md

@@ -0,0 +1,30 @@
+---
+description: One-line Agent Monitor health + counts summary from /api/stats
+---
+
+Fetch the dashboard stats and print a single-line health summary.
+
+Run:
+
+```bash
+curl -s -m 5 http://localhost:4820/api/stats
+```
+
+Then print exactly one line summarizing health and key counts from the JSON,
+in this shape:
+
+```
+✅ UP | 127 sessions | 3 active | 1 agents | 4,892 events | 42 today | 2 ws
+```
+
+Pull the numbers from these fields: `total_sessions`, `active_sessions`,
+`active_agents`, `total_events`, `events_today`, `ws_connections`.
+
+If the `curl` command fails (non-zero exit, empty body, or unparseable JSON),
+print instead:
+
+```
+❌ DOWN | dashboard not reachable at http://localhost:4820 — start it with `npm start` from the repo root
+```
+
+Do not modify any data. Output only the single summary line — no preamble.