test(performance): add J4 search journey (#1816)

* test(performance): add J4 search journey

Measures typing a six-character query into the header search box on
/workspace/search until the global search results settle, on a profile
with the M3U fixture and the mock's existing 12,000-item `large` Xtream
catalog. Counters: bridge calls and SQL statements per search (with a
per-keystroke breakdown), serial IPC depth, DOM mutations, change-detection
ticks, layout shift and long tasks; wall-clock last keystroke to settled
and first keystroke to first result.

Runs in the existing journeys target and the warn-only CI job, whose
summary now prints the per-keystroke table. Moves J3's picsum artwork
blocker into a shared helper.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test(performance): J4 settles only on the final term's query

The probe could settle on cards of an earlier term that stay visible while
the final term debounces. The journey now stamps every dbGlobalSearch trace
event in the main process, and the record requires the last query between
the sentinels to be for the final term and to have completed before the
end sentinel. Iterations with a keydown gap over 250 ms (below the 350 ms
debounce) are rejected; gaps and the final query are kept as evidence.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test(performance): anchor J4's SQL count to the journey sentinels

renderer.sqlStatementsPerSearch was the difference of test-side samples
taken before the first key and after the end sentinel had been read, so
database work in either gap could be counted. The main process now reads
main.sqlStatements when the start and end sentinels arrive, and the counter
is their difference; sqlStatementsAfterSettled starts at the end sentinel.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: 4gray <fourgray@proton.me>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -296,8 +296,8 @@ jobs:
         if: needs.performance-journeys-scope.outputs.run == 'true'
         runs-on: ubuntu-latest
         # The electron-performance build is the bulk of the time; each journey
-        # (launch, open-source, playback) is six fresh Electron processes plus
-        # one seeding run.
+        # (launch, open-source, playback, search) is six fresh Electron
+        # processes plus one seeding run.
         timeout-minutes: 30
         # Warn-only for the first two weeks of plan item B3: a failure is
         # visible on the run but does not fail the workflow.