JJ-FZF 0.32.0.nightly2508160046

Development version - may contain bugs or compatibility issues.

.github/workflows/testing.yml: update artifact name in GitHub workflow    # 2025-08-16 Tim Janik 7f2c4ec

.github/workflows/testing.yml: add build step for self-extracting jj-fzf.sfx    # 2025-08-16 Tim Janik 9360e32

Makefile.mk: add Makefile rule to build self-extracting archive for jj-fzf    # 2025-08-16 Tim Janik cb67fb8
    This commit introduces a new Makefile rule to generate a self-extracting
    archive (SFX) for jj-fzf. The SFX archive bundles the jj-fzf script with
    all its installation files into a single executable shell script.

sfx.sh: add self-extracting shell script generator    # 2025-08-16 Tim Janik 5f0f8bb
    This commit introduces sfx.sh, a self-extracting shell script utility that
    packs a binary executable and its dependencies into a single, self-contained
    shell script. The script embeds a tarball containing all necessary files,
    which is extracted at runtime into a temporary directory. The embedded
    script then executes the packed binary from that temporary location.

Makefile.mk: add `artifacts` to `CLEANDIRS`    # 2025-08-16 Tim Janik 48926a7

Full Changelog: v0.32.0...v0.32.0.nightly2508160046