test(gbrain-detect): include gbrain_pooler_mode in schema regression (PR #1591)

PR #1591 (PgBouncer transaction-mode detection, @mikeangstadt) added
gbrain_pooler_mode to the gstack-gbrain-detect JSON output but did not
update the schema regression check in
test/gstack-gbrain-detect-mcp-mode.test.ts. Adding the key in alphabetical
order matching the rest of the schema array. Downstream sync-gbrain ignores
unknown keys, so this is forward-compat.

Without this, the test fails with a diff:
  + "gbrain_pooler_mode"
because keys is the actual set returned and the expected array was
pre-#1591.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

test/gstack-gbrain-detect-mcp-mode.test.ts

@@ -267,6 +267,10 @@ describe('schema regression', () => {
       'gbrain_local_status',
       'gbrain_mcp_mode',
       'gbrain_on_path',
+      // PR #1591 added gbrain_pooler_mode for PgBouncer transaction-mode
+      // detection. Keep alphabetized; downstream sync-gbrain ignores unknown
+      // keys so adding here is forward-compat.
+      'gbrain_pooler_mode',
       'gbrain_version',
       'gstack_artifacts_remote',
       'gstack_brain_git',