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).

server/lib/tmux.js

@@ -1,9 +1,9 @@
 /**
  * @file tmux.js
  * @description Thin wrapper around the `tmux` CLI for the terminal-run
- * feature. Every dashboard-managed session is named `ccam-lane-<id>` (see
+ * feature. Every dashboard-managed session is named `agenthub-lane-<id>` (see
  * `pty-run.js`) so a real terminal can attach to the exact same session with
- * `tmux attach -t ccam-lane-<id>` (or `ccam lanes shell`). Never builds a
+ * `tmux attach -t agenthub-lane-<id>` (or `agenthub lanes shell`). Never builds a
  * shell string — every call is `execFileSync("tmux", [...argv])` with an
  * explicit argument array (matches this repo's rule for git in worktree.js).
  * The one place a command line is composed is `sendCommand`, which types into
@@ -53,9 +53,9 @@ function envFlags(env) {
  * if tmux itself fails to start (caller decides how to surface that).
  *
  * `env` becomes tmux `-e NAME=value` pairs, which tmux puts in the pane's own
- * environment (tmux >= 3.2). The dashboard uses it for CCAM_LANE_ID so a `ccam`
+ * environment (tmux >= 3.2). The dashboard uses it for AGENTHUB_LANE_ID so a `agenthub`
  * call from inside the pane knows exactly which lane it belongs to instead of
- * guessing from cwd — see resolveLaneArg in bin/ccam.js.
+ * guessing from cwd — see resolveLaneArg in bin/agenthub.js.
  */
 function newSession({ name, cwd, argv, env }) {
   execImpl(["new-session", "-d", "-s", name, "-c", cwd, ...envFlags(env), "--", ...argv]);