fix(config): negative cache age must miss, not hit

Registry.from_url checked `if age < cache_max_age_seconds` to
decide cache hit/miss. On Windows, the freshly-renamed cache file
sometimes reports an `st_mtime` slightly in the future of
`time.time()` due to filesystem-time vs wall-clock precision skew.
That made `age` negative, which (correctly per <) satisfied any
positive `cache_max_age_seconds`, but also incorrectly satisfied
`cache_max_age_seconds=0` — turning the documented "always
refetch" semantic into "use stale cache".

Tightened to `0 <= age < cache_max_age_seconds`. Negative ages now
trigger a refetch on every platform; positive ages behave
unchanged.

Surfaced by tests/test_remote_registry.py::test_from_url_refresh_
bypasses_cache on windows-latest after the matrix cleanup in
56c3bfd exposed Windows runners (previously all queued behind ARM).

Author: imanimanyara

src/get_installer/config.py

@@ -274,7 +274,12 @@ def from_url(
             cache_path = cd / f"registry-{key}.json"
             if cache_path.is_file():
                 age = _time.time() - cache_path.stat().st_mtime
-                if age < cache_max_age_seconds:
+                # Reject negative ages: on Windows (and some FUSE mounts)
+                # st_mtime can land slightly in the future after a rename
+                # because of filesystem-time vs wall-clock precision skew.
+                # `cache_max_age_seconds=0` must always bypass the cache,
+                # so guard the comparison from below.
+                if 0 <= age < cache_max_age_seconds:
                     try:
                         data = json.loads(cache_path.read_text(encoding="utf-8"))
                         return cls.from_dict(data, source_path=cache_path)