Convert a cache key to a filesystem-safe filename via UTF-8 -> base64url.
Zarr keys can include non-ASCII group/array names, so the key is
encoded to UTF-8 bytes before base64url conversion. The output
filename is safe across all browser OPFS implementations.
Bumping OPFS_ENCODING_VERSION invalidates any directory persisted
with a different output; loadMetadata treats it as a cold cache.
(The move of every dataset directory under the luxar/ namespace dir —
see opfs-root.ts — needed no bump: pre-namespace directories at the
OPFS root are simply never read again.)
Convert a cache key to a filesystem-safe filename via UTF-8 -> base64url.
Zarr keys can include non-ASCII group/array names, so the key is encoded to UTF-8 bytes before base64url conversion. The output filename is safe across all browser OPFS implementations.
Bumping OPFS_ENCODING_VERSION invalidates any directory persisted with a different output; loadMetadata treats it as a cold cache. (The move of every dataset directory under the
luxar/namespace dir — seeopfs-root.ts— needed no bump: pre-namespace directories at the OPFS root are simply never read again.)