test(resource-manager): repair the merge-call ratchet anchor

The ambiguous-id fix added `ambiguousWorktreeIds` after `worktreeById` in the
mergeSnapshotAndSessions call, so the parity test's end anchor no longer matched:
indexOf returned -1 and slice(start, -1) silently widened the scan to the rest of
the file. The test still passed but stopped pinning the merge call site.

Verified: removing `...resourceSessionBindings` now fails the test again.

src/renderer/src/components/status-bar/resource-session-classification-parity.test.ts

@@ -16,7 +16,7 @@ describe('resource session classification parity', () => {
     const source = readFileSync(DERIVED_MODEL_PATH, 'utf8')
     const mergeCall = source.slice(
       source.indexOf('mergeSnapshotAndSessions(resourceSnapshot'),
-      source.indexOf('worktreeById\n          })')
+      source.indexOf('ambiguousWorktreeIds\n          })')
     )
 
     expect(mergeCall).toContain('...resourceSessionBindings')