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/commands/agenthub-doctor.md

@@ -0,0 +1,33 @@
+---
+description: Diagnose a plugin-installed AgentHub — Node, bootstrap, server, hooks, CLI, MCP build
+---
+
+Run the diagnostic and report what it found. Do not fix anything unless the user
+asks.
+
+```bash
+node "${CLAUDE_PLUGIN_ROOT}/scripts/plugin-doctor.js"
+```
+
+Print the output verbatim, then add at most three lines of guidance based on the
+`FAIL` and `WARN` rows:
+
+- `FAIL Node` → the installed Node is too old for `node:sqlite`; the server
+  cannot start until Node is upgraded.
+- `FAIL Hooks` → duplicate hook entries double every token and cost figure.
+  Starting a new Claude Code session removes them automatically (the bootstrap
+  backs the file up as `settings.json.agenthub-bak` first).
+- `FAIL Server` or `FAIL Runtime deps` → run `/agenthub-update`, then check
+  `~/.claude/agent-dashboard/runtime/bootstrap.log` and `server.log`.
+- `FAIL MCP build` → `mcp/build/` is out of date; run `npm run mcp:build` in a
+  checkout and commit it.
+- `WARN agenthub CLI` → print the exact `export PATH=...` line from the output.
+- `WARN Skill plugins` → the pipelines name slash commands no installed plugin
+  provides. The dashboard is unaffected; `/agenthub:ship-feature(-lane)` is what
+  stops partway. The bootstrap normally installs these itself, so this row also
+  means that attempt has not run or did not succeed — say `/agenthub-update` retries
+  it, and print the `claude plugin install …` line from the output as the manual
+  route.
+- `WARN Dashboard UI` → run `/agenthub-open` to build the bundle.
+
+No preamble, no summary of things that passed.