Expose configured-zone fetch diagnostics

[backslash-f]

Summary

• fail an explicit freshness request when its configured zone reports a per-zone fetch error
• log privacy-safe database, zone, fetch-reason, and dirty-state diagnostics
• add coordinator and formatter regression coverage
• document the diagnostic and failure contract

Validation

• swift test (46 tests)
• Swift Format format-and-lint
• AgentGuidelines consumer validation 0.0.32
• git diff --check

Runtime purpose

This is the first evidence-gathering layer for the owner-private manual-fetch failure. It does not reset CKSyncEngine state or mutate CloudKit topology.