docs: establish public alpha onboarding

[WindDAnalytics]

Summary

Establishes the stranger-facing public-alpha onboarding path for QuantumD.

This change:

• rewrites the repository landing page
• makes the published quickstart the dominant first action
• documents the exact TestPyPI artifact and checksum
• prevents dependencies from resolving through TestPyPI
• explains the Evidence Graph and trust boundary in plain language
• exposes the five-evaluator program
• adds public-alpha release documentation
• removes stale pre-release and roadmap language
• adds evaluation and release pages to documentation navigation

Validation

• 32 regression tests passed
• strict documentation build passed
• the documented TestPyPI wheel checksum passed
• the built-wheel public-alpha acceptance gate passed
• unsigned governed execution failed closed
• local trust remained simulator-only
• poisoned cloud credentials were isolated
• all ten independent evidence checks passed
• repository stability passed

Visibility

This pull request does not change repository visibility or GitHub settings.
The repository remains private until final launch configuration is complete.