Expose the first-run mobile gate and release v0.6.2

[udhawan97]

What changed

• portalled the required first-run audience modal to document.body
• kept the post-choice Easy/Expert toggle inside responsive header chrome
• added a contract that pins the modal boundary
• bumped the immediate hotfix to 0.6.2 with changelog, release notes, Current State, and Decision Log updates

Why

The public v0.6.1 installed-wheel smoke exposed a fresh-mobile containment defect. The compact Menu is closed by default at 320px, but the native audience dialog was nested inside it. showModal() opened the backdrop while the ancestor's display:none hid the dialog, leaving an invisible page-wide blocker.

PyPI artifacts are immutable, so this must be an immediate 0.6.2 superseding release rather than a replacement 0.6.1 artifact.

Impact

A genuinely fresh narrow run now shows the audience choice, advances to coach marks, then exposes the compact Menu. Parser, graph, checks, persistence, provider, and progress behavior are unchanged.

Verification

• fresh isolated data directory at 320×800: visible audience modal → choice → coach → Menu
• no horizontal overflow and zero console errors
• 236 Python tests and Ruff
• all web contracts plus production SPA build
• Astro check and production build
• Graphify refresh and scoped query
• wheel/sdist checksums, byte-identical bundled SPA index, isolated wheel version smoke