errcheck flagged six naked defer Close() calls in the pack code and its
tests. Wrap them in the same defer func() { _ = x.Close() }() form the rest
of the tree already uses.
BuildZIM walks a cloned host directory, turns every file into a content
entry with a MIME inferred from its extension, picks a main page, and adds
the standard metadata plus a mainPage redirect. state.json is skipped.
BuildBinary appends the archive to a copy of kage behind a KAGEPCK1 trailer,
and Embedded detects that trailer at startup so the binary serves itself.
Handler maps / to the main page and /path to a content entry, the same
handler the embedded viewer uses.
Duc-Tam Nguyen