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).

client/src/components/workflows/__tests__/LanePipelinePanel.test.tsx

@@ -132,7 +132,7 @@ describe("LanePipelinePanel", () => {
     statsMock.mockResolvedValue({ pipelines: [], lanes: [] });
     render(<LanePipelinePanel />);
 
-    expect(await screen.findByText(/ccam lanes add/)).toBeInTheDocument();
+    expect(await screen.findByText(/agenthub lanes add/)).toBeInTheDocument();
   });
 
   it("refetches narrowed to the lane picked, and falls back to a cwd for an untitled one", async () => {
@@ -162,7 +162,7 @@ describe("LanePipelinePanel", () => {
     // the whole subtree, so a handle grabbed before it is already detached.
     await waitFor(() => expect(screen.queryByTestId("pipeline-stat-plan")).not.toBeInTheDocument());
     expect(screen.getByTestId("pipeline-stats-lane-picker")).toBeInTheDocument();
-    expect(screen.queryByText(/ccam lanes add/)).not.toBeInTheDocument();
+    expect(screen.queryByText(/agenthub lanes add/)).not.toBeInTheDocument();
   });
 
   it("surfaces a failed fetch", async () => {