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/openapi.js

@@ -1265,8 +1265,8 @@ function createOpenApiSpec() {
             format: {
               type: "string",
               description:
-                'Bundle format marker (always "ccam-export" for exports from this version).',
-              example: "ccam-export",
+                'Bundle format marker (always "agenthub-export" for exports from this version).',
+              example: "agenthub-export",
             },
             version: { type: "integer", description: "Bundle schema version.", example: 1 },
             exported_at: { type: "string", format: "date-time" },
@@ -1863,12 +1863,12 @@ function createOpenApiSpec() {
                 "text/plain": {
                   schema: { type: "string" },
                   example:
-                    "# HELP ccam_up 1 when the dashboard API is serving this scrape.\n" +
-                    "# TYPE ccam_up gauge\n" +
-                    "ccam_up 1\n" +
-                    "# HELP ccam_sessions Number of sessions by lifecycle status.\n" +
-                    "# TYPE ccam_sessions gauge\n" +
-                    'ccam_sessions{status="active"} 3\n',
+                    "# HELP agenthub_up 1 when the dashboard API is serving this scrape.\n" +
+                    "# TYPE agenthub_up gauge\n" +
+                    "agenthub_up 1\n" +
+                    "# HELP agenthub_sessions Number of sessions by lifecycle status.\n" +
+                    "# TYPE agenthub_sessions gauge\n" +
+                    'agenthub_sessions{status="active"} 3\n',
                 },
               },
             },