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/__tests__/plugin-doctor-skill-plugins.test.js

@@ -1,7 +1,7 @@
 /**
  * @file Tests the `Skill plugins` row of scripts/plugin-doctor.js — the check
  * that tells a fresh install its pipelines name slash commands no installed
- * plugin provides (today: `superpowers`, which `/ccam:ship-feature-lane` drives
+ * plugin provides (today: `superpowers`, which `/agenthub:ship-feature-lane` drives
  * step by step). The row must WARN and never FAIL: without that plugin the
  * dashboard, hooks, CLI and MCP all still work, so failing a doctor run over it
  * would cry wolf. Every case runs against an injected temp CLAUDE_HOME.
@@ -14,7 +14,7 @@ const fs = require("node:fs");
 const os = require("node:os");
 const path = require("node:path");
 
-const TMP_HOME = fs.mkdtempSync(path.join(os.tmpdir(), "ccam-doctor-skills-"));
+const TMP_HOME = fs.mkdtempSync(path.join(os.tmpdir(), "agenthub-doctor-skills-"));
 process.env.CLAUDE_HOME = TMP_HOME;
 
 const { diagnose } = require("../../scripts/plugin-doctor");