1. Persist taskPermissions in HistoryItem so permissions survive task
restarts. Added taskPermissions field to historyItemSchema, included
it in taskMetadata output, and restored it in the Task constructor
when loading from history.
2. Add ReDoS mitigation for model-provided regex patterns:
- isSafeRegex() heuristic rejects nested quantifiers like (a+)+
and overlapping alternations in repeated groups like (a|a)+
- Max pattern length capped at 200 characters
- Both checks enforced at schema validation time via Zod refinements
- 11 new tests covering ReDoS detection and persistence round-trips
eb256220e7