fix: restore CI and safe docs deployment

[MateoBodon]

Resolves the independent portfolio audit's Microalpha findings.

• repairs the repository-wide Ruff/Black/isort debt so CI reaches substantive tests
• keeps the source-formatters consistent through shared configuration
• changes the documentation quickstart to clone and source-install this repository
• explicitly warns that pip install microalpha is an unrelated PyPI project
• grants the Docs workflow the minimum contents: write permission and uses strict builds
• dates the latest completed economic ledger as 2026-07-11 and distinguishes newer infrastructure work
• moves compact evidence/claim boundaries into the first screen
• replaces the obsolete docs-link test with a public install-safety contract

Local verification: 128 passed, 1 deselected; 77% coverage against a 75% gate; Ruff, Black, isort, detect-secrets baseline, and strict MkDocs build passed.

The public docs link remains disabled until this PR is merged, the corrected site is deployed, and the live rendered page is verified.