fix(studio): tolerate SkillSpace skill metadata

[richarddancin]

Summary

• fetch SKILL.md from SkillSpace package metadata when the detail response omits inline content
• normalize legacy SkillSpace SKILL.md frontmatter so YAML-sensitive descriptions do not crash debug generation
• relax local skill upload validation to the minimum needed for packaging: require SKILL.md and safe paths, but do not reject name/description formatting locally

Tests

• npm test -- markdownPromptEditor.test.mjs
• ./.venv/bin/python -m py_compile veadk/cli/generated_agent_skills.py tests/cli/test_generated_agent_backend_codegen.py tests/cli/test_generated_agent_backend_codegen_extended.py tests/cli/test_frontend_skill_spaces.py veadk/cli/cli_frontend.py
• direct Python metadata repro for legacy SkillSpace frontmatter and relaxed local skill materialization
• npm run build

Note: pytest and ruff are not installed in the local venv, so I could not run those exact local commands before opening the PR.