tests: add complete guard pipeline test suite (OuroborosEntropyGuard,…

[borjamoskv]

Summary

Adds a comprehensive async test suite for the guard pipeline, covering:

• OuroborosEntropyGuard – import check, entropy cancellation, pipeline no-silent-failure
• HealthGuard – import check, write-safety passes when healthy, blocks when degraded (HealthSLAViolation)
• StorageGuard – import check, write-safety passes when healthy
• Integration smoke test – verifies all guards are discoverable in the module tree

All tests use pytest-asyncio and unittest.mock.AsyncMock; guards that are not yet importable are skipped gracefully.

Closes #412

[github-actions]

∞ MÖBIUS — PR Analysis

Metric	Value
Files changed	1
Total changes	220 (+/-)
Complexity	high
Est. review time	30 min
Has tests?	✅
Has Rust changes?	No

Labels applied: tests

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