feat(FN-882): add loop detection recovery with compact-and-resume

- Add ContextLimitDetector to detect agent loops via repeated tool call patterns
- Implement compact-and-resume strategy: summarize conversation and restart agent from current step
- Add loop recovery to StuckTaskDetector with configurable attempt tracking and retry limits
- Extend executor with automatic loop recovery on context limit detection
- Add loop recovery support to pi executor with same compact-and-resume pattern
- Add comprehensive tests for context-limit-detector, stuck-task-detector loop detection, executor, and pi recovery
- Add changeset for patch bump to @gsxdsm/fusion
- Update README with loop detection and recovery documentation

.changeset/fn-882-loop-recovery.md

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+"@gsxdsm/fusion": patch
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+Add loop detection recovery with compact-and-resume for stuck agents. When the stuck task detector identifies a looping agent (active but not making step progress), it now attempts an in-process compact-and-resume before falling back to kill/requeue. Context-limit errors from LLM providers are also caught and trigger compaction.