feat: streamline AI document toolbar and add PDF export

[kwp-lab]

Summary

• simplify the AI document toolbar and remove the redundant regenerate action
• allow generating another document or version from the same scene template
• move generation, Markdown copy, PDF export, and other actions into a clearer icon-first toolbar
• export polished PDFs with Markdown styling and syntax highlighting, using the document H1 for both the filename and PDF title
• expose an "open folder" action after PDF export
• bump Nota to 0.10.0 and update documentation, licenses, notices, and SBOM

Testing

• npm run check
• frontend: 17 test files, 134 tests passed
• Rust: 130 passed, 5 environment-dependent tests ignored