Fail closed on invalid telemetry files

[jackwener]

Summary

• reject telemetry.json when the top-level value is not a telemetry object
• reject unknown-section objects and known telemetry sections with non-array values
• keep partial legacy files with known array sections readable
• add regressions that verify invalid bytes are not overwritten

Verification

• npm --workspace @maka/storage test
• npm run build
• git diff --check