refactor: rename typed methods to task_storage and add batch lookup
- Rename lookup_typed_meta/data to lookup_task_storage_meta/data
- Move serialize helpers out of trait into standalone functions
- Add batch_lookup_task_storage_meta/data with default implementations
- Add test for serialize helpers roundtrip
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>