Add Ubuntu 26.04 resolute support

[houssemexo26]

Add Ubuntu 26.04 "Resolute" as a supported base image track alongside the existing Noble (24.04) and Jammy (22.04) tracks.

Changes:

• main.yml: add resolute-* tag prefix → ubuntu:26.04 mapping
• scheduled-build.yml: add Resolute matrix entry to weekly security rebuild
• prepare.sh: handle DEB822 .sources format (used by Ubuntu 24.04+) alongside legacy sources.list for universe/multiverse activation
• README.md: update component table to reflect multi-track support

[github-actions]

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[houssemexo26]

@samip5 Could you take a look at my PR? Thanks

[samip5]

No as I no longer maintain it.

[Theaxiom]

I am looking at it now.

[Copilot]

Pull request overview

Adds an Ubuntu 26.04 "Resolute" track to the multi-track baseimage build system, alongside the existing Noble (24.04) and Jammy (22.04) tracks. Because 24.04+ ships APT sources in the new DEB822 (.sources) format, prepare.sh is updated to handle both formats when enabling Universe/Multiverse.

Changes:

• Register resolute-* tag prefix → ubuntu:26.04 in the build workflow and add a Resolute entry to the scheduled rebuild matrix.
• Teach prepare.sh to enable Universe/Multiverse in DEB822 .sources files on Ubuntu ≥ 24.04, falling back to the legacy sources.list edits otherwise.
• Update README to reflect the multi-track lineup.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/main.yml	Map resolute-* release tag prefix to ubuntu:26.04; update warning message to list the new prefix.
.github/workflows/scheduled-build.yml	Add a resolute / ubuntu:26.04 entry to the weekly rebuild matrix; bump one actions/checkout use to v6.
image/prepare.sh	Detect Ubuntu ≥ 24.04 and edit DEB822 .sources files; keep legacy sources.list handling for older releases.
README.md	Update component table to mention the 26.04/24.04/22.04 tracks.

Comments suppressed due to low confidence (2)

image/prepare.sh:22

• The DEB822 sed patterns only match exact strings Components: main or Components: main restricted. If the Ubuntu base image's .sources file has any other combination (e.g., Components: main restricted universe, an additional component, or a different order/spacing), neither substitution will match and universe/multiverse will silently remain disabled. The legacy branch above was tolerant via deb.*universe patterns; consider a more robust approach such as parsing/rewriting the Components: line generically (e.g., always appending universe and multiverse if absent) so this doesn't silently break on a future image update.

      sed -i 's/^Components: main$/Components: main restricted universe multiverse/' "$f"
      sed -i 's/^Components: main restricted$/Components: main restricted universe multiverse/' "$f"

image/prepare.sh:23

• The DEB822 branch only edits the Components: line, but the legacy branch also uncommented deb-src lines (the original code's intent stated in the comment on line 13 — "and deb-src for main"). DEB822 source files use a separate Types: deb line; on Ubuntu 24.04 ubuntu.sources defaults to Types: deb (no deb-src). After this change, source packages will not be available on the 24.04/26.04 tracks, which is a behavioral regression relative to the jammy track. Consider also rewriting Types: deb to Types: deb deb-src if deb-src is intended to be enabled.

    # DEB822 format: enable universe and multiverse components
    for f in /etc/apt/sources.list.d/*.sources; do
      sed -i 's/^Components: main$/Components: main restricted universe multiverse/' "$f"
      sed -i 's/^Components: main restricted$/Components: main restricted universe multiverse/' "$f"
    done

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[Theaxiom]

@houssemexo26 Please apply copilot's suggestions and let me know, then I will merge this in.

[houssemexo26]

@houssemexo26 Please apply copilot's suggestions and let me know, then I will merge this in.

Done