v8.6.1-dev.8

• Merge pull request #1610 from kaitranntt/kai/fix/1608-launch-settings-hardening
• docs(cliproxy): document strip-vs-overlay launch-settings siblings and model-key superset
• test(cliproxy): cover launch-settings corrupt-JSON fallback and overlay permissions
• fix(cliproxy): clean up launch-settings overlay on synchronous spawn failure