Roll out SleepStager parity coverage

[bhelm]

Summary

• cover seven owner-qualified SleepStager public operations in the cross-platform differential harness
• add bounded schemas, two deterministic seeds per operation, curated boundary/default cases, and cache-isolation regressions
• lock exact regressions for Swift SleepStager gravity fingerprint aliases distinct axes in detect, V1, and V2 caches #66 and Swift SleepStagerV2 clips shuffled streams before defensive sort #67 while keeping SleepStagerV2: decide the canonical cache clipping padding across platforms #43 quarantined
• remove exactly seven exemptions per platform; preserve upstream StreamFingerprint.gravityQuant platform-test governance

Verification

• 178 Python tests
• parity ledger: no new findings
• ratchet: differential=78, platform-test=63, exempt=2585, errors=0
• fresh full+diff native coverage: Swift 1495 tests, Kotlin full unit suite
• pilot and post-clean: 527 cases, 0 diffs
• stale nonce rejected
• seven semantic mutants detected on each platform
• independent final review: P0/P1/P2 = 0

Test/harness-only; no production-code changes.