perf(electron): compile the main process and preload for ES2022

apps/electron-backend/tsconfig.json now sets target ES2022, so the
main-process bundles, the preloads and the backend's Jest specs no longer
downlevel async/await, optional chaining and nullish coalescing for ES2015.
Electron 43 runs them natively in the main process and in the sandboxed
preload. tsconfig.base.json keeps es2015 because other projects inherit it.
useDefineForClassFields stays false, so class fields keep their constructor
assignment semantics and only syntax changes.

main.js + main.app.js + deferred-events.js + main.preload.js shrink from
2,008,115 to 1,853,599 bytes (-7.7%); every inlined __awaiter helper is gone.
Startup did not move measurably: main-process CPU to did-finish-load and the
J1 launch journey were flat in interleaved A/B runs, with identical counters.

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

apps/electron-backend/tsconfig.json

@@ -4,7 +4,9 @@
         "types": ["node"],
         "moduleResolution": "nodenext",
         "module": "NodeNext",
-        "ignoreDeprecations": "6.0"
+        "ignoreDeprecations": "6.0",
+        "target": "ES2022",
+        "useDefineForClassFields": false
     },
     "include": ["**/*.ts"]
 }

docs/development/electron-debugging.md

@@ -134,3 +134,17 @@ from `app.asar`. The preload is
 [workspace shell](../architecture/workspace-shell.md) for window behavior,
 [DB worker](../architecture/sqlite-db-worker.md) for worker ownership and
 [Electron security](../architecture/electron-security.md) for bridge boundaries.
+
+`apps/electron-backend/tsconfig.json` sets `"target": "ES2022"` for the
+main-process bundles (`main.js`, `main.app.js`, `deferred-events.js`), the
+preloads and the backend's Jest specs; `tsconfig.base.json` stays at `es2015`
+because other projects inherit it. Electron 43 (Node 24 and Chromium's V8) runs
+ES2022 natively in the main process and in the sandboxed preload, so
+async/await, optional chaining and `??` are no longer downleveled.
+`"useDefineForClassFields": false` keeps the class-field semantics of the old
+target (constructor assignment, not `[[Define]]`), so only syntax changed. The
+workers built by `build-worker.js` (esbuild, `node18`) were already native. On
+2026-09-29 the four bundles shrank from 2,008,115 to 1,853,599 bytes (every
+inlined `__awaiter` gone); neither main-process CPU time to `did-finish-load`
+nor the J1 launch journey's wall-clock changed measurably in an interleaved
+A/B, and J1's counters were identical.