## Why
`LambdaDriver` (1.4k lines) and `LocalDriver` (709 lines) each mixed
many unrelated concerns in a single class.
## What changed
**This PR only moves code** — every line is byte-for-byte the same as
`main` (same logic, same comments, same constants, same lock keys/TTLs,
same error mapping). The drivers are now thin orchestrators wiring
co-located sub-services + pure utils (each with unit tests).
| File | Before | After |
|---|---|---|
| `lambda.driver.ts` | 1425 | 252 |
| `local.driver.ts` | 709 | 231 |
| Largest sub-service | — | 371 (`lambda-executor-manager`) |
| Unit tests on these paths | 0 | 15 |
Lambda split: `lambda-aws-client` / `lambda-tool-functions` /
`lambda-layer-manager` / `lambda-executor-manager` + `constants` +
`types` + 5 pure utils.
Local split: `local-layer-manager` / `local-child-process-runner` /
`local-prebuilt-bundle` + `constants` + `types` + 3 pure utils.
No behavior change, no signature change, no public-API change.
