feat: implement ecosystem contract and prepare v3.0.1

[Foscat]

Summary

• implement the reviewed three-library ecosystem contract and ownership boundaries
• publish Layout manifest/personality metadata and package the complete documentation set
• point npm metadata to the live GitHub Pages demo and align readable/minified entrypoints
• prepare patch release 3.0.1 with immutable UI bootstrap compatibility
• secure the release toolchain dependency graph with zero audit findings

Compatibility

• minimum: ui-style-kit-css 2.1.0 / interactive-surface-css 1.5.0 / layout-style-css 3.0.0
• candidate current: ui-style-kit-css 2.1.0 / interactive-surface-css 1.5.0 / layout-style-css 3.0.1
• UI fixture: bdbb6a7e432f30b92de206cac6a00fe85394190c

Verification

• 22/22 static and contract tests
• Chromium, Firefox, and WebKit full demo matrices
• current and minimum seven-combination ecosystem matrices
• six curated snapshots with zero differing pixels
• 45-file npm pack and 28 resolved export specifiers
• full and production-only audits: zero vulnerabilities
• npm publish dry-run for layout-style-css@3.0.1

No public export was removed and no breaking CSS behavior changed.