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-productivity/commands/whats-next.md

@@ -0,0 +1,20 @@
+---
+description: Suggest the next action from your most recent in-progress sessions and recent errors.
+argument-hint: "[project-path]"
+---
+
+Recommend what to pick up next, using Agent Monitor data at `http://localhost:4820`. If the dashboard is unreachable, tell the user to start it with `npm start` from the repo root.
+
+Optional **$ARGUMENTS**: a project path (`cwd`) to scope the suggestion to one project; otherwise consider all recent work.
+
+1. Fetch recent sessions: `curl -s 'http://localhost:4820/api/sessions?limit=20'` (already sorted most-recently-updated first).
+2. For the most recent unfinished sessions (`status` of `running`, `error`, or `abandoned`), fetch their events to see where they left off:
+   `curl -s 'http://localhost:4820/api/events?session_id=<id>'` — look at the last few events (last `tool_name`, `summary`, and any `APIError` / `Compaction` event types).
+
+Print a short, prioritized "Next up" list (top 3–5 items). For each item give:
+
+- The project (`cwd`) and session status.
+- What it was last doing (from the final events / last tool used).
+- A concrete suggested next action (resume, debug the error, re-run after compaction, or close out).
+
+Put unresolved errors and abandoned-mid-task sessions at the top. Keep it to one screen and cite only data returned by the API.