Add self-contained catalog entry skills

[andyluo7]

What changed

Adds three source-owned, self-contained agent-skill packages under agent-skills/:

• quark-install: environment inspection, install planning, verification, and recovery
• quark-torch-ptq: PyTorch/Hugging Face PTQ planning, execution, export, and layered validation
• quark-onnx-ptq: ONNX PTQ, calibration, provider checks, AutoSearch budgeting, and layered validation

Each package includes only portable skill frontmatter plus its own references, UI metadata,
and executable inspection helper. All relative links remain inside the package. The skills do
not reference .claude/skills-impl, call another Quark skill, or depend on a catalog-specific
wrapper/importer.

Why

Quark's existing .claude/skills surface is intentionally backed by a detailed internal
orchestration graph. External catalogs should not couple themselves to that private layout,
internal skill names, or a release-specific resolver.

This separate agent-skills/ distribution surface gives Quark a small set of stable entry
points that an external catalog can copy unchanged with a generic source importer. The existing
17 internal skills are not modified.

This is the source-side prerequisite for the redesign requested on amd/skills#122. That catalog
PR will remain paused until these source-owned entry points are accepted, after which it can be
reduced to generic source declarations and generated imports.

Validation

• generic quick_validate.py passes for all three skills
• uvx ruff check agent-skills
• uvx ruff format --check agent-skills
• python3 -m py_compile agent-skills/*/scripts/*.py
• environment collector smoke test
• Torch and ONNX inspector CLI/failure-path smoke tests
• local Markdown links resolve and remain within each skill package
• git diff --check

Review focus

• whether the three entry-point boundaries are the right long-lived public surface
• whether agent-skills/ is the right source-owned distribution path
• whether any Quark 0.12 technical guidance should be corrected before catalog federation