feat(retro): add agent-scaffolding skill to retro harness

Give the retro agent access to the agent-scaffolding skill so it can
reference scaffolding principles when ideating improvements from
retrospective analysis.

Assisted-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Ralph Bean <rbean@redhat.com>

Author: ralphbean

internal/scaffold/fullsend-repo/harness/retro.yaml

@@ -20,6 +20,7 @@ host_files:
 skills:
   - skills/retro-analysis
   - skills/finding-agent-runs
+  - skills/agent-scaffolding
 
 pre_script: scripts/pre-retro.sh