Fix Rust doctest failures (#95909)
## Summary
- Fix Rust documentation examples so workspace doctests compile
successfully.
- Mark incomplete illustrative snippets as ignored while keeping
runnable examples checked.
- Update stale imports and API usage, and classify directory trees as
text.
## Verification
- cargo fmt --all -- --check
- cargo test --workspace --doc --no-fail-fast
- autoreview --mode local --stream-engine-output (Codex + Claude: 0
findings)
