Spec drift: opinion — new GET /market/slug/{slug} endpoint missing from spec

[realfishsam]

Summary

Opinion Trade added a new endpoint GET /market/slug/{slug} that allows fetching a market by its human-readable slug rather than by numeric ID. This endpoint is not in core/specs/opinion.yaml and is not called by the Opinion adapter.

Impact

MEDIUM — PMXT cannot look up Opinion markets by slug. This is useful for deep-linking and for matching markets to external references that use slugs rather than IDs.

Details

• Endpoint: GET /market/slug/{slug}
• Path parameter: slug (string) — the market's URL slug (e.g. trump-wins-2026)
• Response: same Market object schema as GET /market/{id}
• Spec file: core/specs/opinion.yaml

Required Fix

1. Add GET /market/slug/{slug} to core/specs/opinion.yaml with correct path parameter and response schema
2. Consider whether the Opinion fetcher should use this endpoint for market lookups when a slug is available