Harden the ML ebook for safer public release

[rkalani1]

Summary

• Clarify the license boundary: ISC for repository code, CC BY 4.0 only for publisher-controlled book content and cleared assets.
• Add third-party notices, contribution/security policies, citation metadata, asset rights records, an SBOM, and a dated publication review.
• Correct and review all 20 chapters, replace weak-provenance figures with semantic HTML/CSS, and tighten accessibility and responsive behavior.
• Add hash-locked dependencies and fail-closed release gates for source, provenance, secrets, rendered output, active content, external egress, MathJax integrity, and exact deployment revision.

Validation

• 27/27 adversarial release-gate mutation tests passed.
• 24/24 ebook structural tests passed.
• 96 bounded numerical/source checks passed.
• Exact committed build passed: 24 HTML pages, 9.67 MiB, release SHA e6b00b0.
• Gitleaks 8.30.1 scanned 576 reachable commits and about 489.21 MB of Git text with no detected leak.
• Runtime, audit, and bootstrap lock audits found no known vulnerabilities; CFF and CycloneDX SBOM validation passed.

Release hold

Draft only. Do not merge or deploy until the owner confirms:

1. the right to license the text, code, current images, and applicable AI-assisted output;
2. UW, sponsor, employment, commissioned-work, and affiliation obligations;
3. that no patient/source data or third-party confidential material was used; and
4. whether to retain the existing public Git history or replace it with a clean-history publication repository.

This PR does not rewrite history. Historical assets were screened with bounded automated methods, not full raster OCR, source-data reconstruction, visual-similarity clearance, trademark clearance, or a legal chain-of-title opinion.