Phase 1: Database migration for new ArchiveResult fields
- Add output_str (TextField) for human-readable summary
- Add output_json (JSONField) for structured metadata
- Add output_files (JSONField) for dict of {relative_path: {}}
- Add output_size (BigIntegerField) for total bytes
- Add output_mimetypes (CharField) for CSV of mimetypes
- Add binary FK to InstalledBinary (optional)
- Migrate existing 'output' field to new split fields
Phase 3: Update run_hook() for JSONL parsing
- Support new JSONL format (any line with {type: 'ModelName', ...})
- Maintain backwards compatibility with RESULT_JSON= format
- Add plugin metadata to each parsed record
- Detect background hooks with .bg. suffix in filename
- Add find_binary_for_cmd() helper function
- Add create_model_record() for processing side-effect records
Phase 6: Update ArchiveResult.run()
- Handle background hooks (return immediately when result is None)
- Process 'records' from HookResult for side-effect models
- Use new output fields (output_str, output_json, output_files, etc.)
- Call create_model_record() for InstalledBinary, Machine updates
Phase 7: Add background hook support
- Add is_background_hook() method to ArchiveResult
- Add check_background_completed() to check if process exited
- Add finalize_background_hook() to collect results from completed hooks
- Update SnapshotMachine.is_finished() to check/finalize background hooks
- Update _populate_output_fields() to walk directory and populate stats
Also updated references to old 'output' field in:
- admin_archiveresults.py
- statemachines.py
- templatetags/core_tags.py
