Support `$.flags` context values in segment conditions

Support `$.flags..` conditions.

### Acceptance criteria

- The engine dependency is bumped to the version supporting `$.flags` context values.
- `getFlags` passes segments to the engine so identity-less evaluation resolves `$.flags` and `$.environment` conditions.

Start at the getFlags entry point and the project’s engine dependency declaration. Verify how segments are passed during identity-less evaluation, then run the existing test suite or relevant segment-condition tests; done means the engine version supports $.flags and $.environment conditions and getFlags resolves them without an identity.

索引モデルが issue の本文から書いたものです。