Genre, Subgenre, and Audience Tags on Works

### Feature Request

System-wide support for first-class genre tags on Works (books), including schema, admin/type registry, API changes, UI/UX, editing, autocomplete, search/index, data migration, and developer/user documentation.

### Breakdown

1. Update olclient/schemata/work.schema.json (and infogami type registry) to support genres: List of Tag (tag_type: genre)
2. Ensure API/backend changes propagate to/from infogami + storage
3. Add display of genres (as labeled chips) to templates/type/edition/view. html and work.html
4. Update editing UI for genres: input, add/remove chip JS, autocomplete, CSS
5. Canonicalize genre tag UX style & shape; document, get agreement
6. Implement dedicated genres autocomplete using `/tags.json?tag_type=genre`
7. Update Solr schemas, update Solr updater logic, ensure search/facet by genre
8. Write tests (schema, UI, API, Solr), migration/backfill script
9. Add developer and end-user documentation. Plan for upgrade/feature flag, Solr reindex.
- See full checklist in ticket for complete file-by-file breakdown and gotchas.