feat: add durable private job logs

[vitry]

Summary

• add private durable per-job logs beside persisted job records, with exact-owner detailed status exposing only the canonical log path
• archive every accepted safe semantic progress event while preserving four-entry previews and excluding raw tool data, reasoning, files, credentials, and capabilities
• coordinate foreground, background, resume, recovery, SessionEnd, and Transfer terminal logging with cross-process append locks and authoritative result winners
• document privacy and retention semantics and keep source/marketplace payloads byte-identical

Safety

• logging remains observational and cannot change success, failure, cancellation, recovery, or result-artifact authority
• compact, foreign-owner, sibling-session, bound Rescue, relay, and terminal projections do not expose log paths
• no --log flag or log-reading command is introduced
• logging failures emit only one fixed safe diagnostic and never expose paths or raw errors

Test Plan

• npm run check:line-endings
• npm run lint
• npm run typecheck
• npm test — 1,568 passed, 3 opt-in skipped; marketplace build 2/2 passed
• final Standards review: 0 findings
• final Spec review: 0 findings