proj-v1: absolute matchup projection challenger (distribution + full ladder)

A THIRD challenger (after arch-v1, contact-v1), MLB batting v1. Champion is
market-relative P(stat>LINE); proj-v1 is ABSOLUTE — what the hitter will DO —
emitted as a full distribution from which the WHOLE LADDER (P≥1,P≥2,P≥3) derives.
Champion untouched; nothing claimed; the ledger decides per rung, per stat.

- projection/distribution.js — Bayesian Gamma-Poisson → negative-binomial
  predictive. Admits over-dispersion; under-dispersion → Poisson approx
  (conservative, documented). Uncertainty scales with sample by construction
  (r=α): thin → WIDE (real mass on P≥1, honestly thin P≥3), thick → tight.
  NEVER abstains — width carries the honesty.
- projection/matchupRead.js — the input the book doesn't use. HONEST FIDELITY:
  pitcher repertoire is rich (97% pitch-mix) but hitters have NO pitch-type
  performance, so TRUE repertoire-vs-profile is impossible today. This is the
  COARSE version (arsenal buckets fastball/sinker/breaking + whiff/hard-hit
  tendency × hitter whiff/chase/gb-fb/hard-hit) — beats generic L/R, derived +
  documented + TESTED two-sided. A hitter pitch-type feed unlocks the true form.
- projectionChallenger.js — park RELATIVE to the player's own log exposure
  (isHome→own park, away→opp park; Phase B's raw-multiply bug solved), recency-
  weighted fit, per-factor breakdown (form/park/weather/platoon/matchup — show
  your work), full rung set + book-implied per rung. Combined non-form
  multiplier bounded.
- Wired after contact-v1, own try, flag PROJ_V1_ENABLED, reusing arch-v1's
  already-computed park/weather/platoon (no duplicate env I/O). Own ledger
  columns (migration 032, applied to prod): distribution, ladder, point, line,
  our-P, book-implied, factor breakdown — measurable per rung/stat after settle.

Phase 0 (prod-verified): venue join via isHome; NB family; uncertainty-as-width;
coarse matchup honest fidelity; no lineup-slot (per-game rate, volume implicit).
Sanity: thin-hot → wide (credible low rung, thin high rung); .300 hitter ≠ 3.0;
matchup two-sided; champion byte-identical. proj-v1 suites 23/23; snapshot/
ledger/siblings 74 green. Forward-only, version-stamped, PROJ_V1_ENABLED kill.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCNgGSt5qvcLxaeQqa7Zpj

supabase/migrations/032_projection_challenger.sql

@@ -0,0 +1,19 @@
+-- proj-v1 — ABSOLUTE MATCHUP PROJECTION CHALLENGER (MLB batting).
+-- A THIRD challenger (after arch-v1 p_win_challenger, contact-v1 p_win_contact),
+-- in its OWN columns so the full rung set + per-factor breakdown + our-P-vs-book
+-- comparison stay independently measurable, per rung, per stat, after settle.
+--
+-- The champion projects P(stat > line); proj-v1 projects what the hitter will DO
+-- as a full distribution (negative-binomial), park-RELATIVE to the player's own
+-- exposure, matchup-aware (coarse repertoire-vs-profile). It never abstains —
+-- thin sample → wide distribution. Additive + forward-only: pre-nomination rows
+-- carry null proj_version. Champion and settled/locked grades untouched.
+alter table ledger_entries
+  add column if not exists proj_version       text    null,
+  add column if not exists proj_point         numeric null,
+  add column if not exists proj_line          numeric null,
+  add column if not exists proj_p_over_line   numeric null,
+  add column if not exists proj_book_implied  numeric null,
+  add column if not exists proj_distribution  jsonb   null,
+  add column if not exists proj_ladder        jsonb   null,
+  add column if not exists proj_factors       jsonb   null;