Runtime and launch contract

Implemented interfaces for the optional standalone runtime.

Configuration

Setting	Contract
CAMPLY_RUNTIME_MODE	distributed (default) or standalone; independent of auth/environment.
CAMPLY_DB_DRIVERNAME	Standalone requires sqlite+aiosqlite; reject PostgreSQL/in-memory SQLite.
CAMPLY_DB_HOST	Preserve existing SQLite path config; test absolute file paths.
CAMPLY_FRONTEND_DIR	Optional absolute built-asset directory; otherwise packaged assets.
CAMPLY_HEARTBEAT_INTERVAL	Existing 300-second default; validate > 0.
CAMPLY_TARGET_COOLDOWN	Existing 55-second default; validate > 0.
Auth/session settings	Existing meaning/secure defaults; configure frontend origin explicitly.

Standalone does not construct broker/Prometheus clients. Missing index.html, unreadable assets, unwritable database, invalid settings, and conflicting worker settings fail before serving. Supported launch uses one Uvicorn worker without production reload. A second instance sharing the database is unsupported.

Task / launcher

• task standalone:install: Install backend core and frontend build tools without infrastructure extras or all-workspace sync.
• task standalone:build: Build root assets with relative /api, stage in backend/packages/backend/backend/static, and build existing workspace package wheels into backend/dist without Docker. Include assets in the backend wheel.
• task standalone:run: Select standalone, apply Alembic, validate resources, and invoke python -m backend.standalone on port 8000.
• task standalone:test: Verify an isolated core install and service-free browser flow; development tools are test-only.
• python -m backend.standalone: Prepared-artifact launch without Task/Node, with equivalent migrations/lifecycle, one worker, and loopback bind by default. Owners can explicitly configure another host.

Core dependencies: backend → worker/db/providers; worker → db/providers; providers → db. Root distributed extras activate backend/worker Celery/Redis/Prometheus and db psycopg extras. Existing install/tasks/Compose explicitly select distributed extras; installed wheels cannot rely on workspace paths.

Static routing

• /api and /api/... retain API routing/errors.
• /metrics and descendants return 404 standalone, never SPA fallback.
• Actual assets serve files inside the built directory only; missing assets return 404.
• GET/HEAD HTML navigation deep links receive index.html after reserved routes. Non-navigation requests do not receive SPA HTML; unsupported methods retain 405. Reject traversal outside assets.
• Fingerprinted assets cache immutably; entry HTML revalidates.
• Distributed retains separate hosting and metrics.

Common engine boundary

Typed async functions receive explicit sessions/configuration and return typed results or classified failures. No broker, decorators, locks, or metrics imports. Standalone persists intents with results; Celery adapters dispatch existing tasks. Adapters own locking/retry/operational recording.

Installed migration resources

The db wheel must contain the complete Alembic environment and revision graph as package resources. The launcher resolves them independently of the checkout/current directory and builds Alembic configuration programmatically, without development-only post-write hooks. Installed-artifact tests must upgrade both empty and populated databases using only installed wheels.