Add apptainer extra

[yarikoptic]

Installs Apptainer following upstream Debian instructions: download the .deb from the apptainer/apptainer GitHub release and install via apt so runtime deps are pulled in. Picks the trixie+ vs default .deb based on /etc/os-release VERSION_CODENAME and fails on non-amd64 (upstream publishes amd64 .deb only).

Wires the new extra through setup-yolo.sh (help, --extras=all expansion, validation regex) and SPEC.md (build args, optional extras, setup script flags).

[github-actions]

pr-scout: spec-audit

✅ Spec update matches code changes

Code change summary

Here's a summary of the new or changed functionality:

• The Docker image build process can now optionally install Apptainer (version 1.4.5) if the build argument EXTRA_APPTAINER is set to "1". This functionality is currently limited to amd64 architecture.
• The setup-yolo.sh script now recognizes "apptainer" as a valid option for the EXTRAS argument.
• When the EXTRAS argument in setup-yolo.sh is set to "all", the "apptainer" component is now automatically included for installation.

Verdict

PASS

The spec update accurately describes all the user-visible code changes.

• The addition of EXTRA_APPTAINER as a Dockerfile build argument is covered.
• The APPTAINER_VERSION build argument and its default value are documented.
• The recognition of apptainer as a valid option for setup-yolo.sh's --extras argument is included.
• The automatic inclusion of Apptainer when --extras=all is used in setup-yolo.sh is implied by its addition to the list of "Predefined extras" for that argument.
• The amd64 architecture limitation for Apptainer installation is correctly specified.
• The Apptainer version (1.4.5) is consistently mentioned.

[yarikoptic]

any objections or desires @asmacdo ?