Stage-2 entry point for the First Run use case. Adds the
`ara_first_run` Lambda package mirroring the `postcode_splitter`
template, its typed trigger contract, and a stub `FirstRunPipeline`.
- `AraFirstRunTriggerBody`: thin command of five fields — `task_id`,
`sub_task_id` (UUID, lifecycle), `portfolio_id`, `property_ids`,
`scenario_ids` (int business IDs). No `model_config` override, so
Pydantic's default `extra="ignore"` lets the FastAPI backend add
fields without breaking deployed lambdas. UPRNs / Scenario defs are
deliberately off the event — read from source-of-truth tables.
- Thin `handler.py`: validate-and-delegate only, via a named
`dispatch_first_run` seam (testable without the Lambda runtime).
Subtask status (in-progress/complete/failed) + CloudWatch log URL
come for free from the existing `@subtask_handler()` decorator.
- `FirstRunPipeline` (orchestration/) stub: `run(command)` receives the
validated command. Declares a structural `FirstRunCommand` Protocol
(the three business fields) that `AraFirstRunTriggerBody` satisfies,
so orchestration needs no application-layer import — rhymes with the
`EpcFetcher`/`SolarFetcher` Protocols on IngestionOrchestrator
(ADR-0011). Full Ingestion→Baseline→Modelling composition lands in
#1136.
- Dockerfile / requirements.txt / local_handler/ mirror postcode_splitter.
TDD: 7 new tests (trigger-body validation incl. forward-compat +
id-types, pipeline seam, handler delegation). pyright strict clean.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
