fix(runtime): accept interaction request digests

[drewstone]

Fixes #858.

Retained response commands now validate only the exact run coordinates. Their request digest identifies the interaction request, so the provider validates it against its durable interaction record.

Proof:

• pnpm exec vitest run src/runtime/retained-run.test.ts — 37/37 passed
• pnpm run typecheck — passed
• pnpm exec biome check src/runtime/retained-run-binding.ts tests/helpers/retained-run-child.ts — passed

The restart integration now answers with the digest from the replayed canonical interaction instead of the retained turn digest.

[tangletools]

✅ Auto-approved drewstone PR — 2070172d

This PR was opened by the trusted drewstone account.
The full PR reviewer audit still runs separately and will publish findings if it detects issues.

This approval is provisional. It rests on the audit running. If the audit cannot run — for example the CLI bridge rejects it — this approval is dismissed rather than left standing, so an unrun check never reads as a passing one.

_{tangletools · auto-approval · reason: drewstone_author · 2026-08-15T05:43:56Z}