Validate local Skill workflow integration

[cyou1314]

Summary

• Adds validate-skill-integration to cross-check a metadata-only local Skill adapter against a project workflow.
• Verifies stage ownership, Skill labels, output contracts, evidence semantics, required producers, and action-request routing.
• Adds high-confidence checks for credential fields and values, email addresses, and local/network paths without echoing detected values.
• Extends documentation, CI, and verify-examples, and prepares version 0.2.4.

Why

The adapter and workflow were previously valid only as separate documents. A mismatched stage or unsafe project handoff could therefore pass both validators independently. This change makes the public interface enforceable end to end while keeping local Skill implementation private.

Boundary

A passing integration check is not a full privacy guarantee. Manual review remains mandatory. The command does not copy or execute local Skills, render or generate media, inspect artifacts, perform final QC, or demonstrate community adoption.

Validation

• Local aigc-project-prompt-loop companion update passed the official Skill structure validator and routing guard checks; it is not included in this public PR.
• python -m unittest discover -s tests — 54 passed
• aigc-director-kit validate-skill-integration ... --json — passed
• aigc-director-kit verify-examples --root . — 13/13 passed
• Ordinary non-editable install, installed CLI version/commands, compileall, pip check, and git diff --check passed.