docs: prepare CORNETO 1.0.0 RC5

[pablormier]

Summary

• make the root landing page self-contained and compatible with CORNETO 1.0
• serialize Pages publication into one guarded gh-pages update
• validate switcher URL/version metadata and preserve version ownership boundaries
• enforce canonical committed release notes before publishing a tag

Compatibility

No CORNETO Python API changes.

Validation

• 502 tests passed, 34 skipped
• strict Sphinx build passed with warnings treated as errors
• Ruff check and format gate passed
• Poetry package build and Twine checks passed
• landing asset validation and simulated main/tag Pages deployments passed