Make Woolpack onboarding executable

[minglong51]

Summary

• make the public Woolpack scaffold hand off to exact-version uvx render and strict-lint commands while checkout shims stay on workspace source
• replace checkout-only pack authoring copy across the README, package guide, contributor guide, agent contract, and fallback submission template
• document Python/uv prerequisites and the standalone-versus-cross-pack validation boundary
• bump the package, application pin, lock entry, and design contract to 0.1.1 so the merged fix is release-ready

Verification

• 15 passed in tests/test_pack_lint.py
• targeted Ruff check passed for packages/woolpack/src/woolpack/scaffold.py
• design-doc audit passed
• public source and checkout-shim scaffold/render/strict-lint flows each produced 13 PASS · 0 WARN · 0 ERROR
• uv lock --check and locked sync passed with only the Woolpack lock entry changed
• woolpack 0.1.1 wheel and sdist built; Twine strict checks passed
• git diff --check and public-repo redaction scan passed

Documentation

Updated the product README, Woolpack package README, pack format guide, contributor flow, fallback submission template, AGENTS command contract, and the existing LLD version pin. No architecture diagram changed because module, data, and deployment boundaries are unchanged.

Known follow-up

PyPI 0.1.0 is immutable and still prints the old bare follow-up commands. This PR prepares 0.1.1 but does not tag, release, or publish it. The external index and fallback validator pins should move only after 0.1.1 exists.

Woolroom main currently has an unrelated Ruff 0.16.4 failure across pre-existing files; that broad migration is intentionally outside this PR.