Build an adversarial-PHI red-team corpus and harness for the redactor

[maziyarpanahi]

Description

Adds a synthetic adversarial-PHI corpus and an offline redaction harness that turns the threat-model abuse catalog into an executable leakage gate. The harness reports per-case, per-attack, and per-abuse-case bypass rates, counts processing failures as bypasses, optionally enforces a fail-closed CI threshold across every bucket, and keeps report artifacts free of source and output text.

Type of Change

• New feature (non-breaking change which adds functionality)
• Documentation update
• Test addition/improvement

Changes Made

• Add eight synthetic cases covering obfuscated identifiers, homoglyphs, zero-width splits, full-width and locale format edges, checksum decoys, combining marks, and role-played leakage requests.
• Add a local-only corpus runner with strict schema validation, bounded inputs and outputs, protected-surface matching, PHI-safe atomic reports, per-attack and per-abuse-case aggregation, and optional threshold exits.
• Package the canonical corpus in both source and wheel distributions so the default runner works after installation.
• Reject duplicate keys and assertions, non-finite or invalid UTF-8 JSON, unsafe identifiers, unsupported fields, and comparison values that normalize to an empty surface.
• Add focused harness tests and operator documentation, including strict corpus rules and CI usage.

Testing

• Full test suite: 7,296 passed, 48 skipped
• Focused harness suite: 30 passed
• Real cached offline corpus run: 8 cases, 0 bypasses, zero-rate threshold passed
• Source and wheel builds passed; installed-wheel corpus loading verified
• Formatting, lint, type checking, strict documentation, and scoped pre-commit checks passed

Documentation

• Added the adversarial corpus and harness guide
• Added public API docstrings
• Added the guide to documentation navigation

Dependencies

• No new dependencies

Checklist

• Read the contributing guidelines
• Commits have clear, descriptive messages
• Changes are focused on the red-team harness and its distribution surface

Related Issues

Closes #870

Screenshots/Examples

Not applicable; this change has no UI surface.