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/lanes/__tests__/LaneCard.test.tsx

@@ -265,7 +265,7 @@ describe("LaneCard — the lane's own application stack", () => {
     slot: 3,
     kind: "managed" as const,
     hooks: ["boot", "health"],
-    profileDir: "/work/demo/.ccam/profile",
+    profileDir: "/work/demo/.agenthub/profile",
     services: [{ name: "web", pid: 4242, alive: true }],
     ports: { api: { port: 8003, expected: 8003, listening: true } },
     steppedAside: false,
@@ -350,7 +350,7 @@ describe("LaneCard — integration badges", () => {
       provisioned: true as const,
       up: false,
       slot: 1,
-      profileDir: "/work/demo/.ccam/profile",
+      profileDir: "/work/demo/.agenthub/profile",
       ports: {},
     } as unknown as LaneRuntime);
     vi.mocked(api.lanes.integration).mockImplementation((_id, name) =>
@@ -381,7 +381,7 @@ describe("LaneToolsMenu", () => {
       provisioned: true as const,
       up: false,
       slot: 1,
-      profileDir: "/work/demo/.ccam/profile",
+      profileDir: "/work/demo/.agenthub/profile",
       ports: {},
     } as unknown as LaneRuntime);
   });