Support `$.flags` context values in segment conditions

Support `$.flags..` conditions.

### Acceptance criteria

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

No files or tests are named. Start by locating the engine dependency configuration and the identity-less evaluation entry point; then inspect existing segment evaluation tests. Done means the dependency supports $.flags and identity-less evaluations pass segments so both $.flags and $.environment conditions resolve.

Written by the indexing model from the issue text.