Bundled workflow skills: add behavioral QA beyond schema validation

[islee23520]

Source

• docs/roadmap-reality-lock.md says skill schema validation passes, but behavioral quality of individual skills still needs workflow-level QA.

Current state

Skills/tools/validate-skills.sh validates structure/schema. It does not prove every bundled workflow behaves correctly in target projects.

Acceptance criteria

• Define workflow-level smoke checks for the key bundled skills under Skills/skills/.
• Validate at least Unity workflow behavior through a real supported surface.
• Partial/planned engine workflow skills report blockers instead of mock success.
• Release gate distinguishes schema validity from behavioral readiness.