fix(installer): use EqualFold for binary lookup

Replace manual lowercase comparisons with strings.EqualFold to satisfy staticcheck without changing the installer binary matching behavior.

Signed-off-by: jimyag <git@jimyag.com>

feat(registry): load local package overlays

merge ~/.config/jd packages over the builtin registry by package name.
document local registry files and cover the load path in tests.

Signed-off-by: jimyag <git@jimyag.com>

fix(installer): avoid 'text file busy' error by using rename or unlin…

…king before copy

fix(registry): use bash -c for command mode packages to improve scrip…

…t compatibility

fix(registry): correct inner_path for nettrace package

build(ci): inject GitCommit during goreleaser build