feat: apply DevsLab OSS identity to editor-ruler

[jlc488]

Summary

• apply public oss-brand v0.1.1 O01 identity across the site and all adapter READMEs
• add local favicon, Apple icon, OG metadata, accessible brand links, and responsive light/dark atmosphere
• gate exact assets and metadata through the standard verify command
• preserve every editor adapter demo and runtime behavior

Verification

• full typecheck and 110 tests passed
• Pages build and version/build checks passed
• 390px dark and 195px reflow passed without overflow
• independent final review: spec/code/design PASS

Canonical guide: https://devslab.kr/brand/open-source/