Release Scriveno 2.8.0

[hannsxpeter]

Summary

• Add installer surface profiles, dry-run planning, and surface management commands.
• Add proof-unit workflow, context-health signals, export check mode, and publish preflight guidance.
• Remove standalone source-product naming, update command inventory to 115, and bump package metadata to 2.8.0.

Verification

• npm run release:check
• git diff --check
• standalone source-product name scan