feat: add github pages site scaffold

[costiash]

Agent-Logs-Url: https://github.com/costiash/CognivAgent/sessions/ecb9b441-bb6f-433f-8f29-44ee329844ae

Summary

Brief description of what this PR does.

Related Issue

Closes #(issue number)

Type of Change

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature causing existing functionality to change)
• Documentation update
• Refactoring (no functional changes)
• Tests (adding or updating tests)

Changes Made

• Change 1
• Change 2
• Change 3

Testing

Describe how you tested these changes:

1. Test scenario 1
2. Test scenario 2

Screenshots (if applicable)

Before	After
[screenshot]	[screenshot]

Checklist

• My code follows the project's code style
• I have run uv run pytest and all tests pass
• I have run uv run mypy . with no errors
• I have run uv run ruff check . with no errors
• I have updated documentation if needed
• I have added tests for new functionality
• My commits follow the commit message convention
• I have not committed sensitive data (API keys, passwords)

Additional Notes

Any additional information reviewers should know.

[claude]

This PR adds a GitHub Pages landing page. See full review below.

[claude]

PR Review: feat: add github pages site scaffold — This PR adds a GitHub Pages landing page with a deployment workflow, SEO metadata, and a polished static site. No backend/app code touched. Positive: Well-structured workflow (path-scoped triggers, concurrency control, workflow_dispatch). Strong SEO (OG, Twitter Card, JSON-LD, canonical URL, robots.txt, sitemap.xml). Responsive design (980px/720px breakpoints). Security-conscious messaging. Issues: (1) PR description empty - fill in template. (2) Stale test count - page shows 914 but README says 910, use 900+. (3) External links open in same tab - add target=_blank rel=noopener noreferrer. (4) No favicon - add cognivagent-icon.svg to docs/. (5) Missing skip-to-content link for a11y. (6) Preload critical Google Font for LCP. (7) Add sitemap link in HTML head. (8) sitemap.xml has single entry - add guides if needed. (9) No environment protection on workflow - fine for docs. Security: Static HTML only, no XSS surface, permissions correctly scoped, no secrets. Summary: Solid scaffold. Main items: fill PR description, fix test count, add target blank to external links.