refactor(app): consume shared indexing core, remove duplicated indexer (Phase 5d-3c-i)

The desktop app now indexes through the shared provider adapters + persist
layer (scripts/providers/{claude,codex}, scripts/persist, scripts/parsing)
instead of maintaining its own parallel indexer. buildIndex shrinks from
~1173 to ~592 lines, eliminating the skill<->app parse duplication that
Phase 5 set out to remove. electron-vite bundles the .ts core from source
with better-sqlite3 injected; the provider->parsing graph stays
node:sqlite-free so nothing drags node:sqlite into the app.

Also fix a misleading log: when a manual rebuild tears down the worker
mid-build, the cancelled background build is a deliberate stop, not a
failure. Guard the service's failure log with the stopped flag so it no
longer prints "Obelisk index build failed: Indexer worker stopped" on
every rebuild.

- CONTEXT.md: provider-adapter + single-persist + node:sqlite-free parsing.
- docs/adr/0005: app builds with electron-vite (TS+ESM), packages with
  electron-builder; preload CJS for sandbox; app consumes core from source.

Verified: full suite 121/121; a node:sqlite-adapter dogfood of the rebuild
path over real data (969 files, 285 sessions, FTS rebuilt) runs clean; app
Rebuild confirmed in real Electron/better-sqlite3.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/adr/0005-app-electron-vite-ts-esm.md

@@ -0,0 +1,39 @@
+# The app builds with electron-vite (TS + ESM), packages with electron-builder
+
+**Context.** The desktop app must consume the shared TypeScript/ESM Core
+(`providers/*` + `persist`) instead of maintaining its own duplicate indexer, and
+the app itself should be TypeScript + ESM long-term. The app previously ran raw
+CommonJS on Electron's Node with only the Vue renderer built by Vite; the main
+process had no build step, and Electron's bundled Node (20 on Electron 33) can
+neither strip TypeScript nor use `node:sqlite`. Options for the main-process build
+were a hand-rolled tsc/esbuild step, `vite-plugin-electron`, or `electron-vite`.
+
+**Decision.** Adopt **electron-vite** to build all three processes (main, preload,
+renderer) as TypeScript + ESM, and keep **electron-builder** for packaging
+(dmg/nsis/AppImage). electron-vite is purpose-built for the Electron three-process
+model and handles the parts a DIY build would force us to hand-maintain forever
+(per-process module format, native-module externalization, dev reload). Specific
+decisions within this:
+
+- **Preload is emitted as CommonJS** even though the app is ESM: the sandboxed
+  renderer (sandbox is on by default since Electron 20, and we keep it on for
+  security) does not support ESM preload. Source stays ESM; only the preload
+  output format is CJS. `main` loads `../preload/index.js`.
+- **The app consumes the Core from source**: electron-vite/rollup bundles
+  `scripts/providers/*` + `scripts/persist` (and their `scripts/parsing.mjs`
+  dependency) into the app's main/worker build, injecting `better-sqlite3`. This
+  works because the provider→parsing import graph is node:sqlite-free (ADR-0001),
+  so nothing drags `node:sqlite` into the app. The `dist/` from `build:core`
+  (ADR-0003) remains for the skill artifact; the app does not need it.
+- **better-sqlite3 stays the app's binding**, externalized (not bundled) and
+  unpacked from the asar.
+
+**Consequences.** The app is restructured into `src/{main,preload,renderer}` with
+`electron.vite.config.ts`; each main module is a build input so CommonJS-style
+require resolution and the indexer worker (`{ type: 'module' }`) resolve at
+runtime. `npm run dev` is `electron-vite dev`. Tests that loaded app modules moved
+to ESM imports, and `app-main-settings` was rewritten from CJS `Module._load`
+mocking to `node:test` `mock.module` (needs `--experimental-test-module-mocks`).
+A future contributor may be tempted to make the preload ESM or disable the
+sandbox — this ADR records that CJS preload under an on sandbox is the intended,
+secure default.