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/db.js

@@ -460,7 +460,7 @@ db.exec(`
   CREATE INDEX IF NOT EXISTS idx_lanes_session ON lanes(session_id);
 `);
 
-// Managed lanes own a git worktree CCAM created and may be destroyed; adopted
+// Managed lanes own a git worktree AgentHub created and may be destroyed; adopted
 // lanes merely point at a directory the user already had and never may be.
 // Existing rows default to 'adopted', so no lane gains a destructive path by
 // upgrading. Probe each column independently so a partial migration (e.g. process
@@ -546,9 +546,9 @@ try {
 // Migrate: per-lane runtime allocation. `slot` is the small integer every runtime
 // fact derives from (ports now; database name and Redis index later) — the
 // numbering Shipyard gets for free from its fixed lane1..lane9 directories and
-// CCAM, keyed by cwd, has to allocate. `ports` is a JSON map name -> port,
+// AgentHub, keyed by cwd, has to allocate. `ports` is a JSON map name -> port,
 // recording the number a lane ACTUALLY got: the preferred `base + slot` may be
-// taken by something outside CCAM, so the allocator steps aside and the real
+// taken by something outside AgentHub, so the allocator steps aside and the real
 // number has to survive a restart or the next boot would move a live lane.
 //
 // Allocation is lazy — a lane that is only ever watched never takes a slot — so
@@ -571,7 +571,7 @@ db.prepare(
 
 // Migrate: per-feature state (B). `active_feature_id` points at the
 // lane_features row currently "live" (unarchived) for this lane — null for a
-// lane that has never called `ccam feature activate`, which is why this
+// lane that has never called `agenthub feature activate`, which is why this
 // column is nullable and every downstream reader of a lane row is unaffected
 // by its addition. ON DELETE SET NULL, not CASCADE: deleting the ACTIVE
 // feature row (which normally only happens via cascade when the LANE itself