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).

scripts/systemd-service.js

@@ -2,9 +2,9 @@
 /**
  * @file systemd-service.js
  * @description Shared helper for installing/removing a systemd `--user`
- * service that keeps the CCAM dashboard server running across reboots,
+ * service that keeps the AgentHub dashboard server running across reboots,
  * without needing Claude Code (or any other tool) to be started first.
- * Used by both `ccam service install` (checkout installs) and
+ * Used by both `agenthub service install` (checkout installs) and
  * `plugin-bootstrap.js` (plugin installs) so the two paths stay in sync.
  * Linux/systemd only — callers fall back to their existing manual-start
  * path when `systemctlAvailable()` is false.
@@ -16,7 +16,7 @@ const os = require("os");
 const path = require("path");
 const { spawnSync } = require("child_process");
 
-const MARKER = "# ccam-managed-unit — regenerated on install, do not edit by hand";
+const MARKER = "# agenthub-managed-unit — regenerated on install, do not edit by hand";
 
 function unitDir() {
   return path.join(os.homedir(), ".config", "systemd", "user");