fix(sleep): thread-safe backend cache + redact exports

[WODE25500]

Sleep-cycle hardening.

• Guard CliBackend _cache/_tokens with a lock on the opt-in parallel replay path (SKILLOPT_SLEEP_WORKERS>1); the model call stays outside the lock so parallel workers still overlap.
• Redact report.json before staging (redact_secrets).
• Redact harvest --output and --json exports (_redact_deep).
• Add tests for CliBackend caching/thread-safety.

[Yifan Yang (Yif-Yang)]

report.json is now correctly passed through the mapping-aware redactor, but the export-redaction and thread-safety fixes are still incomplete in three places.

1. Harvest output uses _redact_deep(payload), while _redact_deep() only recurses into values and loses the mapping-key context. As a result, _redact_deep({"api_key": "plain-secret", "nested": {"token": "other"}}) returns both secrets unchanged. Please use the existing mapping-key-aware redact_secrets(payload) at every structured output boundary.
2. write_staging() redacts report.json but writes caller-provided report_md verbatim. Edit content/rationale can therefore still expose credentials. Please redact the Markdown before writing it as well.
3. Not all cache/token access uses the new lock: the Pi and OpenCode overrides still inspect and pop _cache directly, and tokens_used() reads _tokens without the lock. More importantly, parallel replay_one() attributes one call's tokens from a shared global before/after total, so overlapping workers can charge another worker's tokens to the wrong result. Please route cache/token access through locked helpers, prevent a failed caller from deleting another caller's successful cache entry, and use call-local accounting for per-result tokens.

Please add boundary-level tests for both harvest output/file and report.md, including nested api_key/token mappings. The concurrency tests should use barriers/events to force overlapping misses and assert exact call/cache/token outcomes, including a concurrent Pi/OpenCode empty-result versus successful-result case. The current immediate echo test does not guarantee overlap and can pass without exercising these races.

[WODE25500]

Yifan Yang (@Yif-Yang) — thank you for the thorough review and guidance! I've addressed the feedback:

• Structured outputs now use the mapping-key-aware redact_secrets (not _redact_deep, which loses the key context); report_md is also redacted before writing.
• Thread-safety hardened: cache/token access goes through locked helpers (_cache_get/_cache_pop/_cache_pop_if); tokens_used() is locked; a failed caller only conditionally pops its own empty value (_cache_pop_if), never another worker's success; the base no longer caches empty (transient-failure) results.
• Switched to call-local token accounting (thread-local delta) so parallel replay no longer misattributes tokens through a global before/after total.
• Added tests: nested api_key/token redaction, report.md, barrier-forced concurrency, pop-if not deleting a success, Pi subclass empty-vs-success, and thread-isolated token deltas — all pass.

Thanks again for the detailed review!

[WODE25500]

Yifan Yang (@Yif-Yang) — thank you for the careful review and guidance. In fact I've done almost all of these submissions through DSH, which is exactly why I have a bold idea. Across your recent PR reviews I noticed that you consistently apply a set of quality baselines: fail-closed handling, structure-aware and boundary-consistent redaction, thread-safety with call-local accounting, validating against real contracts, PR hygiene, and so on. I'd like to distill that into a reusable review-standards: a general quality standard plus a pre-PR self-check CLI that contributors run before submitting, so they spend less time on rework and you receive fewer low-quality PRs — a win-win. I'd credit you as the original source of these standards. Looking forward to hearing from you whenever you get a chance.