Add map_feature_names method

[Copilot]

Adds a method that filters features by constraints/preferences and returns Vec<Option<String>> preserving input order — None for filtered-out features, Some(canonical_name) for kept ones. Unlike get_filtered_feature_names which collapses the result, this preserves positional correspondence with the input.

Rust Core

• Trait (provider_trait.rs): Added filter_features to OptionsRegistry
• OptionsProvider (provider_impl.rs): Implemented with same constraint/alias logic as get_filtered_feature_names, pushing None instead of skipping
• OptionsWatcher (watcher.rs): Delegation to inner provider
• Tests (test_provider.rs): Covers no-filter, partial filter, reversed order, and empty input cases

let result = provider.filter_features(&["a", "b"], Some(&preferences))?;
// [None, Some("B")] — "a" filtered out by constraints, "b" kept as canonical "B"

JavaScript (NAPI)

• filterFeatures(featureNames, preferences?) → Array<string | null> on both OptionsProvider and OptionsWatcher

Python (PyO3)

• filter_features(feature_names, preferences?) → List[Optional[str]] on both OptionsProvider and OptionsWatcher
• Also added the previously missing get_filtered_features method to both providers
• Updated .pyi type stubs

Ruby (Magnus)

• filter_features(feature_names, preferences) → Array[String?] on both OptionsProvider and OptionsWatcher
• Registered methods in the init function
• Updated .rbs and .rbi type signatures

me