Function extractStatForProp

Map a DFS prop type string (verbatim from the slip) to the numeric value to compare against the line.

When to use this vs alternatives:

• extractStatForProp (this fn) — concise; returns number | null. Use when you just want the value.
• extractStatForPropViaRegistry — identical, exported from the registry module. Alias.
• extractStatForPropExplained — returns a discriminated union with a reason code on failure. Use when you need to distinguish "unknown prop" from "player DNP" from "league not supported" in UI.

Returns null when the prop type isn't supported by our gamelog source — those legs require manual grading.

Single-stage dispatch via the per-league adapter registry. Inputs are normalised on write, so adapter lookups are exact-match against canonical DfsPropTypeKey strings. Per-league tables live in src/features/bets/dfs-stat-adapters/{basketball,nfl,mlb}.ts; new props go in those tables and the canonical enum, never here.