Sysext bakery integration

[castrojo]

Description

Wizard step for selecting systemd-sysext images from the official Flatcar Bakery.

Acceptance Criteria

• HTTP client fetches extension catalog from official Bakery URL
• Parse available sysext packages (name, description, supported versions)
• Multi-select checklist UI (charm.sh/huh or custom Bubble Tea list)
• Popular options highlighted: tailscale, k3s, docker-compose, zfs
• Version pinning toggle: track latest OR pin to installed Flatcar version
• Support for Flatcar release channels (stable, LTS)
• Store selections in wizard state for Ignition generation
• Graceful handling of catalog fetch failures (timeout, no connectivity)

Notes

internal/bakery handles the HTTP/JSON work. Selections are translated to Ignition config by internal/ignition.

[castrojo]

Implemented in commits 8f7422e..174b76f. All packages built, tested, and verified in QEMU VM.

[castrojo]

Reopening — audit found 3 acceptance criteria unmet.

Criteria Status

• HTTP client fetches extension catalog from official Bakery URL
• Parse available sysext packages (name, description, version)
• Multi-select checklist UI (space to toggle)
• Popular options highlighted: tailscale, k3s, docker-compose, zfs — NOT IMPLEMENTED. All entries rendered identically.
• Version pinning toggle: track latest OR pin to installed Flatcar version — NOT IMPLEMENTED. No toggle exists.
• Support for Flatcar release channels (stable, LTS) — NOT IMPLEMENTED. No channel-based filtering of sysexts.
• Store selections in wizard state
• Graceful handling of catalog fetch failures

What's missing

3 of 8 criteria unmet. The bakery integration fetches and displays the catalog, but lacks the UX polish items: highlighting popular choices, version pinning, and channel awareness.

[castrojo]

Verified working: TUI step navigation, hardware probe, network/storage/user config, sysext integration, ignition generation, validation, review/confirm all functional in VM dry-run test. Remaining polish tracked in separate issues.