docs: restructure the Wrench README

[0thernet]

Summary

• lead the README with Wrench’s mechanism-backed rationale and smallest verified first run
• place observable behavior and important limits before the SDK and deep command reference
• align the wrench.rip hero and install surface with the README architecture
• adopt the shared public README guidelines in the local agent guide

Verification

• bun run website:check
• bun run check functional and omni suites: 3,356 tests passed, 1 intentional skip, 0 failures
• bun run test:standalone outside the filesystem sandbox: passed (the first root invocation reached this final phase but the sandbox blocked its macOS boot-identity sysctl)

Delivery

• changes website source without changing the package version
• production remains release-bound to the immutable website-production release flow; this PR produces only the normal preview until a future versioned release

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
wrench	Ready	Preview	Aug 29, 2026 4:40pm

[0thernet]

Held closed to preserve the serialized Wrench prerequisite and full v0.16.3 release order. The branch and exact README head ee05e1d are preserved for a fresh descendant replay after the release handoff; no unrelated documentation rewrite is merged while the release-control lane is active.