build-app-entry

A legacy feature (has `data/state/` or `services/main-service/`) exposes its `MainService` from `services/main-service/`; compose it from there. Create `src/app/`: - `schema.ts` — the composed plugin: the base feature's `MainService.plugin`, `imports` of the core schema of each feature that loads lazily (single-feature apps skip this). - `versioning/` — `versions.ts` + `versions.test.ts` over the composed schema, when the app persists. - `persistence.test.ts` — a save/load round-trip, when the app persists. - `main.ts` — creates the database, injects every service whose `create` throws, and mounts the root UI. Point `index.html` at it. The how is in the auto-loading `app.md` and `versioning.md` rules, and `features/index.md` (one app, many features).