fix(race): make challenge-link races unrated (no Elo)

[C0derTang]

Closes #302

What changed

src/lib/race/finish.ts only:

• Added const rated = race.challengeToken === null; read off the atomic claim's RETURNING row (right after the claim, before the Elo block).
• Gated the Elo block: if (p2Id) → if (rated && p2Id). Challenge-link races (challengeToken !== null) still finish (claim update runs, outcome/winner recorded, race_finished published), but skip the user load, applyResult, and the entire db.batch — no user Elo/racesPlayed updates, no elo_history inserts, no eloDeltaP1/eloDeltaP2 write. Deltas stay NULL in the DB; d1/d2 stay 0, so the publish carries eloDeltas: {p1: 0, p2: 0} (fine — clients treat the event as a refetch hint and read real, possibly-NULL, deltas from the snapshot; already null-safe per the issue).
• Updated the file-header doc comment and the FinishRaceInput.outcome doc to state Elo only applies to rated races.
• Did not touch the atomic claim / walkover logic. The readyWalkover claim requires non-null readyDeadlineAt (always matchmade ⇒ always rated, since matchmade races always have challengeToken === null), so it's unaffected — added a contrast test proving this.

How verified

• pnpm exec eslint . — clean.
• pnpm exec tsc --noEmit — clean.
• pnpm exec vitest run — 997/997 tests passed across 85 files (full suite, not just this file).
• tests/race-finish.test.ts: all pre-existing fixtures (makeRace() defaults challengeToken: null) pass unchanged (still rated). Added describe("finishRace — unrated challenge races (issue #302)") with:
  1. challengeToken: "abc123" + p1_win ⇒ finished (claim ran, outcome/winner set), zero db.batch calls, zero inserts, zero user selects, publish called exactly once with eloDeltas: {"user-p1": 0, "user-p2": 0}.
  2. Same shape for draw.
  3. Contrast test: challengeToken: null + readyDeadlineAt non-null (matchmade shape) still applies full Elo (batch of 4, 1 insert, 1 select) — pins that the discriminator is the token, not the deadline.

Notes for reviewers

• racesPlayed is deliberately not incremented for unrated races (it drives provisional K-factor in src/lib/elo.ts and leaderboard inclusion in src/lib/leaderboard.ts) — this falls out naturally from skipping the whole batch, no separate logic needed.
• No UI changes — out of scope per the issue; result screens (ResultCard.tsx:295, RaceEndOverlay.tsx:119) are already null-safe for missing deltas.
• No schema changes.

Deviations

None from the issue spec.

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Project	Deployment	Actions	Updated (UTC)
cph2h	Ready	Preview, Comment	Jul 25, 2026 11:44pm