fix: release.yml YAML parse error (0-job startup failure on tag push)

[SoundMatt]

Problem

Every v* tag push produced a red release.yml run with 0 jobs and the message "This run likely failed because of a workflow file issue." The releases themselves exist only because they were created manually with gh release create — the workflow that regenerates safety artifacts (FMEA, TARA, GSN safety case, ISO 26262 / IEC 61508 / DO-178C gap reports, SBOM, audit pack, badge) never actually ran.

Root cause

The "Commit regenerated artifacts" step embedded a multi-line commit message inside a run: | block scalar:

            git commit -m "chore: regenerate safety artifacts for $TAG [skip ci]

Signed-off-by: github-actions[bot] <...>"

The Signed-off-by: trailer sits at column 0. In YAML, a non-indented non-empty line terminates a literal block scalar, so the parser then tried to read Signed-off-by: ... as a mapping key. This is a structural parse error → workflow startup failure with no jobs.

Confirmed with PyYAML against the pre-fix file:

mapping values are not allowed here
  in "release.yml", line 148, column 13

Fix

Build the commit message with two -m flags so every line stays indented within the block scalar:

            git commit \
              -m "chore: regenerate safety artifacts for $TAG [skip ci]" \
              -m "Signed-off-by: github-actions[bot] <...>"

The DCO trailer is preserved (now as a second -m body line).

Validation

• PyYAML parses release.yml, ci.yml, dco.yml cleanly after the fix
• PyYAML confirms the pre-fix release.yml raised the parse error
• CI matrix green on this PR
• After merge: re-tag to confirm release.yml runs green end-to-end