Add story-to-pack research and a structured situation review

Research toward building a content pack from a story corpus, kept on its own
branch and independent of the game. Records the selection experiments against
blind labels, and settles selection as gate G2 followed by a human review:
review.py writes REVIEW.md and a review.json form, apply_review.py checks the
filled form and writes situations.json for the next stage.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01C6UDQ9o6L6Ey173U7XVou6

tools/story-to-pack/probe/embeddings.measure.json

@@ -0,0 +1,42 @@
+{
+ "file": "embeddings.json",
+ "chunks": 838,
+ "rows": [
+  {
+   "k": 25,
+   "sized": 25,
+   "median_dominant": 0.25,
+   "recurring": 21,
+   "coverage": 0.9284009546539379,
+   "tight_recurring": 9,
+   "tight_coverage": 0.2863961813842482
+  },
+  {
+   "k": 40,
+   "sized": 39,
+   "median_dominant": 0.35714285714285715,
+   "recurring": 21,
+   "coverage": 0.7088305489260143,
+   "tight_recurring": 5,
+   "tight_coverage": 0.09069212410501193
+  },
+  {
+   "k": 60,
+   "sized": 55,
+   "median_dominant": 0.5714285714285714,
+   "recurring": 20,
+   "coverage": 0.5501193317422435,
+   "tight_recurring": 3,
+   "tight_coverage": 0.02028639618138425
+  },
+  {
+   "k": 100,
+   "sized": 78,
+   "median_dominant": 0.6666666666666666,
+   "recurring": 16,
+   "coverage": 0.29594272076372313,
+   "tight_recurring": 0,
+   "tight_coverage": 0.0
+  }
+ ]
+}