docs: fix broken Proof Lab CTAs and simplify README first-run path - #175

User-reported problem

The existing raw.githack.com link does not connect for some visitors. README repeated that unreachable URL six times and described it as a live demo.

Changes

• Remove all six raw.githack URLs; use stable repository-relative HTML references rather than pretending a Pages deployment exists.
• Explain the working local demo (counterproof demo) and the forthcoming standalone HTML/Pages path, clearly distinguishing source preview from an already deployed live site.
• Add a short BASE/HEAD evidence diagram and direct navigation to install, Bluefin, Claude oracle case, and third-party evidence.
• Preserve the original hero, badges, technical sections, receipts, and conservative evidence boundaries.

Dependency

Companion PR #173 makes site/standalone.html actually self-contained and adds a GitHub Pages workflow. Merge/deploy/verify #173 before advertising any hosted Pages URL. This README patch is safe even if Pages remains unavailable.

Review checklist

• Render GitHub Markdown and <details> on desktop/mobile.
• Confirm local demo command is valid and README anchors work.
• Verify no claim of an already-live hosted demo remains.

Docs only; no proof engine semantics changed.