fix(fsearch): separate trixie from unstable repo mapping

[mvanhorn]

Summary

Separates Trixie/Debian 13 from sid in the fsearch package definition's case statement, so Trixie uses the Bookworm (12) OBS repo instead of Unstable.

Why this matters

The current mapping (sid|13|trixie -> Unstable) causes fsearch installation failures on Debian 13 because the Unstable OBS repo uses v3 GPG signatures that newer apt versions reject. The Bookworm repo works correctly on Trixie (confirmed by @silentJET85 in #1808).

Changes

• Split sid|13|trixie) DEBIANVER=Unstable into two cases:
  • sid) DEBIANVER=Unstable (preserves existing behavior for sid)
  • 13|trixie) DEBIANVER=12 (uses working Bookworm repo)

Testing

CI package tests will verify the definition is valid.

Fixes #1808

This contribution was developed with AI assistance (Claude Code).

[cubic-dev-ai]

No issues found across 1 file

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Auto-approved: Isolated fix for Debian 13/Trixie repository mapping in fsearch package to resolve GPG signature issues. Low risk and highly specific.}

[philclifford]

We should not kludge this but rather remove support for UPSTREAM_RELEASE where UPSTREAM_CODENAME has a native release upstream as suggested in #1808.

Then the case statement is no longer needed and DEBIANVER can just become UPSTREAM_RELEASE

[mvanhorn]

Reworked per your feedback. Commit 52cba92 removes the UPSTREAM_CODENAME case statement entirely and adds CODENAMES_SUPPORTED="bullseye bookworm jammy noble" so trixie, sid, and newer Ubuntu releases are dropped - fsearch is in the native repos for those now. DEBIANVER is just UPSTREAM_RELEASE directly.

Based on the #1808 discussion where @silentJET85 confirmed trixie and testing both resolve to the native Debian package, and you agreed to de-support those releases.