#3676 refactor(interaction): inline unavailable settle result type

Summary

Remove the extracted unavailable-settle helper's type-only back-reference to its caller. Declare its actual local { observation: SettleObservation } return shape; callers still accept it structurally as SettleOutcome.

One file changed. This follows up the valid import-cycle comment on already-merged #3640. Runtime statements, counter behavior and public fields are unchanged.

Validation

Tested head: 29001081990ea77ebe262ef6bc9ba11ba7ab5ce6 (base 76c1c36ab2).

• pnpm check:affected --base 76c1c36ab2 --head 2900108199 --run: passed.
• Existing unavailable/settle suites: 30 passed.
• Fresh-context review: no findings.

CI checks must finish on this head before merge. No live run is needed for an erased type annotation change.