Complete Story 3.3: Preset Import & Export

Implements FR-19: Preset import/export as JSON

New Files:
- src/core/PresetImportExportManager.js - Core logic for export/import with merge/replace
- src/ui/gm/PresetExportDialog.js - Export dialog with file download
- src/ui/gm/PresetImportDialog.js - Import dialog with file picker, preview, merge/replace
- templates/preset-export.hbs - Export dialog template
- templates/preset-import.hbs - Import dialog template
- styles/components/_preset-import-export.less - Dialog styles
- tests/unit/core/PresetImportExportManager.test.js - 38 unit tests
- _bmad-output/implementation-artifacts/3-3-preset-import-and-export.md - Story file

Modified Files:
- src/ui/gm/DirectorsBoard.js - Added export/import button handlers
- templates/directors-board.hbs - Added Export/Import buttons to footer
- styles/scrying-pool.less - Added stylesheet import
- lang/en.json - Added localization strings for new UI
- _bmad-output/implementation-artifacts/sprint-status.yaml - Story status: review

Features:
- Export all presets from current scene as JSON file
- Import presets with merge (add new, skip duplicates) or replace (overwrite all) modes
- Preview of presets before import with validation status
- Confirmation dialog for replace mode to prevent data loss
- Comprehensive error handling and validation
- All ACs satisfied (AC-9 deferred for README docs)

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

_bmad-output/implementation-artifacts/sprint-status.yaml

@@ -35,7 +35,7 @@
 # - Dev moves story to 'review', then runs code-review (fresh context, different LLM recommended)
 
 generated: "2026-05-21T01:00:00+02:00"
-last_updated: "2026-05-23T15:45:00+02:00"
+last_updated: "2026-05-24T16:30:00+02:00"
 project: video-view-manager
 project_key: NOKEY
 tracking_system: file-system
@@ -63,7 +63,7 @@ development_status:
   epic-3: in-progress
   3-1-save-and-load-scene-presets: ready-for-dev
   3-2-scene-auto-apply-and-confirmationbar: done
-  3-3-preset-import-and-export: ready-for-dev
+  3-3-preset-import-and-export: review
   epic-3-retrospective: optional
 
   # Epic 4: Player Privacy Panel