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/run/LaneConsolePane.tsx

@@ -155,7 +155,7 @@ export function LaneConsolePane({
   const promptPrefill =
     laneTool === "codex"
       ? currentLane?.pipeline_nodes?.length
-        ? `Declare progress as you go: run \`ccam stage <stage> --tool codex --evidence "..."\` immediately at each real transition through this pipeline — ${currentLane.pipeline_nodes.map((n) => n.id).join(" -> ")}. Then, your task:\n\n`
+        ? `Declare progress as you go: run \`agenthub stage <stage> --tool codex --evidence "..."\` immediately at each real transition through this pipeline — ${currentLane.pipeline_nodes.map((n) => n.id).join(" -> ")}. Then, your task:\n\n`
         : ""
       : currentLane?.pipeline_skill || "";
   useEffect(() => {