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).

vscode-extension/extension.js

@@ -1,5 +1,5 @@
 /**
- * @file Main extension file for Claude Code Agent Monitor VSCode extension
+ * @file Main extension file for AgentHub VSCode extension
  * Sets up the extension, registers commands, and manages the status bar item.
  * Implements a dynamic dashboard view that checks for active servers on ports 5173 and 4820.
  * Provides real-time status updates in the sidebar and status bar with background polling.
@@ -40,7 +40,7 @@ function activate(context) {
     async (target) => {
       const panel = vscode.window.createWebviewPanel(
         "agentMonitor",
-        "Claude Code Agent Monitor",
+        "AgentHub",
         vscode.ViewColumn.One,
         { enableScripts: true, retainContextWhenHidden: true }
       );