feat: add podcast and episode music search filters

[luoy16002-svg]

Summary

• add episode and podcast to MusicSearchType
• model their protobuf filter fields and the opaque search-options payload
• include the YouTube Music options required by these two filtered searches
• add deterministic regression coverage for the generated endpoint parameters

Type-only parameters are insufficient for episode searches. The resulting payload now includes the same default search-options suffix used by YouTube Music's filtered endpoints, while existing filter types keep their current encoding.

Fixes #1159

Testing

• npx vitest run tests/main.test.ts -t "encodes the" --reporter verbose
• npm run build
• npm run lint

The targeted tests and full build pass. The full live-API suite completed with 39/40 tests passing; the unrelated existing Innertube#getCourses live test failed against the current upstream response. Manual API checks confirmed both payloads can return 20-result Episodes and Podcasts shelves.