Fix PM-6279 copilot opportunity skill search - #42

Summary

• cast copilot request data to JSONB before JSONB-only skill predicates
• support both legacy upgraded databases with a physical json column and current jsonb schemas
• add focused SQL regression coverage and document the compatibility behavior

Root cause

The search and skills filters assumed copilot_requests.data was physically jsonb. Some upgraded v5 environments retain it as json, so the search COALESCE mixed json and jsonb and the skills predicate called jsonb-only functions with json input. PostgreSQL rejects those expressions and the endpoint returns 500. Project-name-only filtering avoids those expressions, explaining why it continued to work.

Validation

• focused CopilotOpportunityService suite: 14/14 passed
• pnpm lint: passed
• pnpm build: passed
• manual PostgreSQL 17 checks: corrected predicates work against both json and jsonb columns
• full unit suite: 381 passed; the same 15 unrelated failures reproduce on origin/dev
• full end-to-end suite: 73 passed; the same 8 unrelated failures reproduce on origin/dev