fix: derive website CLI version from package metadata

[regenrek]

Why:

• The live generator still copied switchloom@0.3.1 after v0.3.2 was released.
• Unpinning npx would sacrifice reproducibility and allow silent latest-version drift.

How:

• Derive the pinned website CLI version directly from package.json.
• Remove hard-coded version expectations from website tests.
• Refresh current README examples to v0.3.2.

Verification:

• pnpm site:check (65 tests, Astro diagnostics, production build)
• git diff --check