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>

templates/preset-export.hbs

@@ -0,0 +1,29 @@
+<div class="sp-dialog-content">
+  <p class="sp-export-description">
+    {{localize "SCRYING_POOL.ExportPresetsDescription"}}
+  </p>
+
+  <div class="sp-export-info">
+    <span class="sp-info-label">{{localize "SCRYING_POOL.Scene"}}:</span>
+    <span class="sp-info-value">{{sceneName}}</span>
+  </div>
+
+  <div class="sp-export-info">
+    <span class="sp-info-label">{{localize "SCRYING_POOL.PresetCount"}}:</span>
+    <span class="sp-info-value">{{presetCount}}</span>
+  </div>
+
+  <div class="sp-export-info">
+    <span class="sp-info-label">{{localize "SCRYING_POOL.Filename"}}:</span>
+    <span class="sp-info-value sp-filename">{{filename}}</span>
+  </div>
+</div>
+
+<div class="sp-dialog-buttons">
+  <button type="button" class="sp-btn sp-btn-primary sp-export-btn">
+    <i class="fas fa-download"></i> {{localize "SCRYING_POOL.Export"}}
+  </button>
+  <button type="button" class="sp-btn sp-btn-secondary" data-action="close">
+    {{localize "SCRYING_POOL.Cancel"}}
+  </button>
+</div>