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/lanes.js

@@ -523,7 +523,7 @@ function classifyLiveness({ status, stage, ageSec }, deadSec = DEAD_SEC) {
  * only path to `done`.
  *
  * The `current` node is never flagged, even when it has no `stages` entry under
- * its own id: declaring by ALIAS (`ccam stage coding` → the `implement` node)
+ * its own id: declaring by ALIAS (`agenthub stage coding` → the `implement` node)
  * keys `stages` by the raw declared string, so the node the agent says it is on
  * would otherwise render as an inference instead of the blue `current` ring.
  * Past nodes go through `stageRecords`, which resolves those alias keys — a
@@ -550,8 +550,8 @@ function withDetected(states, pipeline, lane) {
  * The inferred stage a lane should be RENDERED at, or null when the lane has a
  * declaration of its own to render.
  *
- * A lane whose sessions never call `ccam stage` — any repo that isn't wired to
- * CCAM — has no declaration at all: `stage` sits on the DB sentinel `idle` and
+ * A lane whose sessions never call `agenthub stage` — any repo that isn't wired to
+ * AgentHub — has no declaration at all: `stage` sits on the DB sentinel `idle` and
  * `stages` stays `{}` forever, so its pipeline map drew 100% pending while
  * detection was quietly tracking every node the agent reached. Such a lane is
  * rendered from its detection instead.