Remove imageDataUrl from active tool runtime paths (Tilemap + Parallax)

- Eliminated `imageDataUrl` usage in `tools/Tilemap Studio/main.js` and `tools/Parallax Scene Studio/main.js`.
- Replaced DataURL import/preview flow with transient `blob:` object URLs (non-persisted), including cache + cleanup/revocation handling.
- Removed fallback branches based on `imageDataUrl` and kept path-based (`imageName`/`imageSource`) as source of truth.
- Updated `tools/shared/projectToolIntegration.js` to stop stripping `imageDataUrl` (no longer present in active tool payloads).
- Verified with `node --check` and repo grep: no `imageDataUrl` usage remains in `tools/` and `samples/` JS/JSON.

Author: DavidQ

samples/metadata/samples.index.metadata.json

@@ -6421,7 +6421,9 @@
       ],
       "toolHints": [
         "tile-map-editor"
-      ]
+      ],
+      "thumbnail": "/samples/phase-12/1209/assets/images/preview.svg",
+      "preview": "/samples/phase-12/1209/assets/images/preview.svg"   
     },
     {
       "id": "1210",
@@ -6446,7 +6448,9 @@
       ],
       "toolHints": [
         "tile-map-editor"
-      ]
+      ],
+      "thumbnail": "/samples/phase-12/1210/assets/images/preview.svg",
+      "preview": "/samples/phase-12/1210/assets/images/preview.svg"  
     },
     {
       "id": "1211",
@@ -6471,7 +6475,9 @@
       ],
       "toolHints": [
         "tile-map-editor"
-      ]
+      ],
+      "thumbnail": "/samples/phase-12/1211/assets/images/preview.svg",
+      "preview": "/samples/phase-12/1211/assets/images/preview.svg"  
     },
     {
       "id": "1301",