Case-insensitive symbol lookup. For symbols that collide across tokens, supply canonicalId to pin a deterministic row, or tokenType as a soft disambiguator; otherwise the largest-supply token wins (and the collision is logged server-side). Returns 404 when the symbol is absent from a resolved snapshot, or when canonicalId is supplied but no row matches that {symbol, canonicalId} pair. During partial outage (stale cache, known symbol) the response carries stale: true; during total outage (fallback cache also empty) returns 503 so clients can distinguish a retryable outage from a permanent 404.

CU cost: 1 CU per request (rwa-supply-detail).