* Add mandatory ZIM metadata for zimcheck
ZIM archives were missing two pieces of metadata that the spec and
zimcheck treat as mandatory: a Description and the Illustrator_48x48@1
favicon Kiwix shows as the book icon. A Name was missing too.
Every archive now writes a Name and a Description, defaulting the
description to a host-derived line when --description is not given. When
the mirror has a usable icon, the favicon is rescaled to a 48x48 PNG and
stored as Illustrator_48x48@1 with an image/png MIME, reusing the icon
discovery and square-fit scaling the app packer already uses.
AddMetadataBytes is added to the zim writer so a binary metadata value
can carry its own MIME instead of being forced to text/plain.
Verified by reading the output back through the libzim engine: all
mandatory keys are present and the illustrator decodes as a 48x48 PNG.
* Update docs for ZIM metadata and current flags
Document the new mandatory metadata in the packing guide and the Kiwix
compatibility note, and default --description in the CLI reference.
While in the reference, bring it back in line with the code: add the
--app and --icon pack flags (shipped in v0.2.0 but never documented),
drop the --max-asset-mb clone flag that does not exist, and fix a stale
--resume mention in the configuration layout.
Add the v0.2.1 release notes and cut the changelog entry.
ZIM is the open single-file archive format Kiwix uses for offline content:
a fixed header, a MIME list, URL/title/cluster pointer lists, directory
entries, zstd-compressed or stored clusters, and a trailing MD5. The writer
lays out a mirror in two passes (assign positions, then emit bytes) and
derives the UUID from the content so packing is deterministic. The reader
random-accesses entries by namespace and url, follows redirects, and reads
xz clusters too so archives from other tooling open.
Cross-checked against an independent reader (gozim): header, MIME list,
namespaces, urls, dirents, and a non-last cluster's blob all read back
byte-for-byte.
Tam Nguyen Duc