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).

docs/superpowers/plans/2026-07-29-workspace-ui.md

@@ -267,7 +267,7 @@ never posts a stage.
 
 ## Out of scope
 
-- Tickets, preview-port links, per-lane credentials, and the `agents`/`creds` buttons from the reference screen — CCAM has no data behind any of them.
+- Tickets, preview-port links, per-lane credentials, and the `agents`/`creds` buttons from the reference screen — AgentHub has no data behind any of them.
 - Any change to `PipelineMap`'s node-state logic, the destroy guard, or the preflight contract.
 - Inferring `done` or a gate outcome. Still forbidden, TTL or not.
 - Re-styling any page other than `/run`.