feat(crossword): add 2025‑12‑21 puzzles and update output generators

- Introduce three new puzzle files for the 2025‑12‑21 theme
- Update main generator to include new data set
- Regenerate pool, report, RSS and theme outputs
- Clean up legacy JSON format in main file
- Ensure consistency across generated assets

out/report.txt

@@ -3,10 +3,10 @@ Feeds: https://feeds.nos.nl/nosnieuwsalgemeen, https://feeds.nos.nl/nosnieuwstec
 Model: mistralai/mistral-nemo-instruct-2407
 
 Master size: 91892
-Theme kept (in master): 10
-Bridge size: 42000
+Theme kept (in master): 36
+Bridge size: 32000
 Shorts kept: 133
-Pool total: 48786
+Pool total: 38805
 
 Enforced minima:
   2: 4000
@@ -19,20 +19,20 @@ Enforced minima:
 
 Counts per length (theme):
   2: 0
-  3: 0
-  4: 0
-  5: 2
-  6: 3
-  7: 2
-  8: 3
+  3: 1
+  4: 6
+  5: 8
+  6: 11
+  7: 4
+  8: 6
 
 
 Counts per length (pool):
   2: 248
   3: 1666
   4: 4850
-  5: 30
-  6: 1957
-  7: 12491
-  8: 27544
+  5: 17
+  6: 432
+  7: 7810
+  8: 23782