The layer compared the server's fetchedAt with the browser's clock, so a
skewed client clock could shift or void the 30-minute window. The proxy now
returns ageMs (its own now minus fetchedAt, at serve time, on fresh, cached
and stale answers); the source refuses a snapshot without a finite,
non-negative ageMs, and the layer dates rows as its now() - ageMs. fetchedAt
stays in the payload for display.
Tests: proxy cached/stale answers report ageMs on the server clock; the
source rejects missing/invalid/negative ageMs; the layer replay test drives
ageMs. qa-gnss stubs send ageMs.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
