feat(ocr): substat-roll validation + rarity inference for GOOD export

Adds the accuracy check yas / Genshin Optimizer use: a substat value is only
legitimate if it equals round(sum of 1..6 rolls) from that stat's roll table.
Values that fit no combination at either rarity are guaranteed OCR misreads.

- src/lib/substatRolls.ts: 5-star roll tables (+ 4-star %/crit tables to tell
  rarities apart), pure isPlausibleSubstat/implausibleSubstats, and inferRarity
  (level > 16 or roll-table fit; conservative, defaults to 5). Validates against
  the union of rarities so valid 4-star pieces are not false-flagged.
- Wired in: shouldFlagArtifactForReview routes implausible substats to review;
  the parser adds an explanatory note; goodInterop export replaces the hardcoded
  rarity:5 with inferRarity (fixes wrong 4-star exports to GO/IK).
- 10 new unit tests; 131 total green; eval still 100%.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lib/goodInterop.ts

@@ -2,6 +2,7 @@ import type { GoodExportArtifact } from "../types/global";
 import type { StoredArtifactRecord } from "../types/storage";
 import { knownSets, mainStatValueReferences, pieceToSet, pieceToSlot } from "./genshinData";
 import { simplifyForMatch } from "./fuzzyMatch";
+import { inferRarity } from "./substatRolls";
 
 // GOOD (Genshin Open Object Description) interop for scanned artifacts, so the
 // local store can round-trip with Genshin Optimizer / Inventory Kamera / Akasha
@@ -127,7 +128,7 @@ export function storedArtifactToGood(record: StoredArtifactRecord): GoodExportAr
   return {
     setKey: setNameToKey(record.setName),
     slotKey: SLOT_TO_GOOD[record.slot] ?? "",
-    rarity: 5,
+    rarity: inferRarity(record.level ?? 0, record.substats),
     level: record.level ?? 0,
     mainStatKey: statDisplayToGoodKey(record.mainStat),
     substats,