Rename max_retries to max_attempts for semantic clarity

[Copilot]

The retry logic used max_retries with semantics that made it behave as a max attempts threshold (1 initial + N-1 retries), causing confusion about whether it meant "total attempts" or "retries after first attempt".

Changes:

• Renamed max_retries → max_attempts in types, consumer logic, and migration
• Updated log messages from "retry X/Y" → "failure X/Y" since retry_count tracks failures, not attempt numbers
• Fixed migration rollback to remove invalid ALTER TYPE ... REMOVE VALUE syntax (PostgreSQL doesn't support enum value removal)

Semantics:

// With max_attempts=3:
// - Attempt 1 fails → retry_count=1, log "failure 1/3"
// - Attempt 2 fails → retry_count=2, log "failure 2/3"  
// - Attempt 3 fails → retry_count=3, mark as permanently failed

The naming now correctly reflects that this value controls total execution attempts, not retry-after-failure count.

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.