Add privileged worker post-probe evidence

[cbusillo]

Summary

• emit a one-time structured event after the isolated schema probe succeeds and before runtime-store construction
• keep diagnostic lifecycle events observable without allowing them to satisfy activation proof
• preserve privileged_operation_worker_poll_succeeded as the only proof-ready worker event
• add focused factory, worker lifecycle, evidence normalization, and target inspection tests

Validation

• uv run --extra dev launchplane ci unittest-shard local (3,078 targets)
• uv run --extra dev mypy control_plane tests
• focused Ruff and format checks
• real PostgreSQL schema-probe/empty-poll and statement-timeout tests
• production container build
• JetBrains production-file inspection: GREEN
• independent review: approved

Refs #2219