[Stack 15/17] Fix D8: match Clojure repful classification (rat > rdt)

[jucor]

Summary

Simplifies the repful ("representative for agree or disagree?") classification
to match Clojure's finalize-cmt-stats (repness.clj:175-177).

Before (Python): 3-branch conditional:

1. pa > 0.5 AND ra > 1.0 → agree
2. pd > 0.5 AND rd > 1.0 → disagree
3. Fallback: whichever metric is higher

After (Clojure): rat > rdt → agree, else disagree.

The old thresholds were redundant — rat and rdt (two-proportion z-scores)
already encode whether the group's agree/disagree rate is significantly higher
than other groups. The simple comparison is both correct and clearer.

Changes

• repness.py: finalize_cmt_stats() — 3-branch logic → rat > rdt
• repness.py: Vectorized — np.select with conditions → np.where(rat > rdt)
• test_discrepancy_fixes.py: Expanded from 2 to 6 tests (including edge cases:
  equal rat/rdt, both negative, both zero)
• Golden snapshots re-recorded (repful direction changes for some comments)

Test plan

• 6 targeted D8 tests pass (rat>rdt, rat<rdt, equal, both negative, both zero, old-vs-new divergence case)
• Full test suite passes (excluding DynamoDB/MinIO tests)
• Private dataset tests pass (--include-local)
• Golden snapshots re-recorded for all 7 datasets
• 19/19 regression tests pass

🤖 Generated with Claude Code

Squashed commits

• Journal: add review session entry (2026-03-17)

commit-id:9ec28252

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Stack:

• [Stack 17/17] Fix K-means k divergence: preserve vote-encounter row order #2524
• [Stack 16/17] Fix D15: match Clojure moderation handling (zero out columns, don't remove) #2523
• [Stack 15/17] Fix D8: match Clojure repful classification (rat > rdt) #2522 ⬅
• [Stack 14/17] Fix D7: match Clojure repness metric formula (product of 4 signed values) #2521
• [Stack 13/17] Fix D6: match Clojure two-proportion test formula (+1 pseudocount) #2520
• [Stack 12/17] Fix D5: match Clojure prop_test formula (Wilson-score-like with +1 pseudocount) #2519
• [Stack 11/17] Fix D9: z-score thresholds from two-tailed to one-tailed #2518
• [Stack 10/17] Fix test DB connection: use DATABASE_URL with dotenv #2517
• [Stack 9/17] Vectorize participant info computation (3-15x speedup) #2516
• [Stack 8/17] Speed up regression tests #2515
• [Stack 7/17] Fix D4: pseudocount formula #2514
• [Stack 6/17] Fix D2: in-conv participant threshold + D2c vote count source #2513
• [Stack 5/17] Per-discrepancy test infrastructure #2512
• [Stack 4/17] Deep analysis of Python-Clojure discrepancies and fix plan #2511
• [Stack 3/17] Speed up CI: replace pip with uv pip in Dockerfile (~2x faster installs) #2510
• [Stack 2/17] Add SKIP_GOLDEN env var to disable golden snapshot tests #2509
• [Stack 1/17] CI: add concurrency group to E2E workflow; run CI on spr/ branches #2508

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⚠️ Part of a stack created by spr. Do not merge manually using the UI - doing so may have unexpected results.