test(performance): add end-to-end Xtream benchmark harness (#1300)

* docs(performance): plan Xtream benchmark

* feat(xtream-mock-server): add deterministic 100k fixture

* style(xtream-mock-server): apply repository formatting

* fix(xtream-mock-server): harden performance fixture data

* feat(xtream-mock-server): add performance control plane

* docs(performance): correct Xtream capture plan

* fix(xtream-mock-server): harden performance controls

* fix(xtream-mock-server): harden control lifecycle

* feat(performance): add Xtream preload markers

* feat(performance): trace Xtream main phases

* feat(performance): mark Xtream store publications

* feat(performance): trace Xtream database phases

* feat(performance): trace Xtream delete cancellation

* feat(performance): capture Xtream phase attribution

* feat(performance): mark Sources Xtream refresh

* test(performance): define Xtream benchmark evidence contracts

* test(performance): add Xtream benchmark runner

* test(performance): surface failure evidence writes

* test(performance): align database read clock

* test(performance): preserve capture failure contracts

apps/electron-backend-e2e/src/performance/worker-request-performance.spec.ts

@@ -55,7 +55,7 @@ function requestTransport(
 ) {
     return {
         ipcCallId: 7,
-        operation: 'DB_GET_CONTENT',
+        operation: 'DB_HAS_CONTENT',
         operationId: 'operation-42',
         operationIdUnavailableReason: null,
         performanceCapture,
@@ -227,7 +227,7 @@ test('main capture retains raw request identity, timestamps, metrics, and reason
     assert.match(source, /ipcCallId: request\.identity\.ipcCallId/);
     assert.match(source, /identity: request\.identity/);
     assert.match(source, /performanceCapture:\s+message\['performance'\]/);
-    assert.match(source, /sourceEpochMs: request\.identity\.sourceEpochMs/);
+    assert.match(source, /sourceEpochMs:\s+request\.identity\.sourceEpochMs/);
     assert.match(source, /captureGeneration: state\.captureGeneration/);
     assert.doesNotMatch(
         source,