Safe-outputs JSON serialization escapes && as \u0026\u0026 and breaks compiled workflows

[mnkiefer]

gh-aw@v0.87.8 corrupts GitHub expressions inside safe-output JSON:

target-repo: ${{ condition && value || fallback }}

GitHub rejects the generated workflow with unexpected character '' while lexing expression. marshalSafeOutputsConfig() uses Go's json.Marshal, which HTML-escapes &.

Use jsonutil.MarshalCompactNoHTMLEscape and add regression coverage ensuring safe-output expressions preserve &&.