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/archive.js

@@ -26,7 +26,7 @@ const crypto = require("crypto");
  * bundles but low enough to stop most zip-bomb attacks from filling disk.
  */
 const MAX_EXTRACT_BYTES = parseInt(
-  process.env.CCAM_IMPORT_MAX_EXTRACT_BYTES || String(4 * 1024 * 1024 * 1024),
+  process.env.AGENTHUB_IMPORT_MAX_EXTRACT_BYTES || String(4 * 1024 * 1024 * 1024),
   10
 );
 
@@ -63,7 +63,7 @@ function safeJoin(root, entryName) {
  * Create a unique temp directory for extraction under the OS tmpdir.
  * Caller is responsible for cleanup via `rmTempDir`.
  */
-function mkTempDir(prefix = "ccam-import-") {
+function mkTempDir(prefix = "agenthub-import-") {
   const dir = path.join(os.tmpdir(), prefix + crypto.randomBytes(6).toString("hex"));
   fs.mkdirSync(dir, { recursive: true });
   return dir;