feat: add GitHub Pages HTML landing page (Issue#5)

[seanseannery]

Key Changes

• Add site/index.html — a fully structured GitHub Pages landing page for the ops CLI tool
• Includes header, hero with CSS-only animated terminal demo, install tabs (Homebrew/npm/curl), getting started usage section, feature cards, links section, and footer
• All copy sourced from README.md
• Tab switching via minimal inline JS as specified
• References ./style.css for styling (to be provided by separate agent)

Why do we need this?

Closes Issue#5. The ops project needs a public landing page hosted on GitHub Pages to improve discoverability and provide a polished first impression for users landing on the project URL. This HTML file provides the complete page structure and content, ready to be styled.

New modules or other dependencies introduced

None. Plain HTML with no build dependencies.

How was this tested?

• Manually reviewed HTML structure against the full spec
• All required class/id names verified present: .site-header, .container, .logo, .site-nav, .hero, .tagline, .cta-buttons, .btn-primary, .btn-secondary, #terminal-demo, .terminal-bar, .terminal-dot, .terminal-body, .line, .prompt, .cmd, .out, .cursor, #install, .install-section, .install-tabs, .tab-btn, .tab-content, .code-block, #usage, .usage-section, .opsfile-example, .features-section, .feature-grid, .feature-card, .feature-icon, .feature-title, .links-section, .links-grid, .link-card, .site-footer
• Tab switching JS verified against spec
• All install commands match README.md