feat(clinical): add evidence recency labels

[maziyarpanahi]

Pull Request

Description

Adds deterministic, local-only recency labels for evidence supporting guarded
clinical claims. Explicit evidence and reference timestamps are classified as
current, stale, future-dated, or unknown using configurable thresholds.
Missing or malformed timestamps fail closed to an explicit unknown label.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to work differently)
• Documentation update
• Code refactoring
• Performance improvement
• Test addition/improvement

Changes Made

• Added EvidenceRecencyPolicy, controlled labels, and deterministic single-item assessments.
• Added value-free reports with label counts, review flags, stable JSON/Markdown rendering, and no retained timestamps, claim text, identifiers, or arbitrary metadata.
• Added synthetic coverage for all labels, configurable boundaries, timezone normalization, unknown handling, deterministic serialization, and privacy-safe errors/reports.
• Added the clinical guide, MkDocs navigation, and publication manifest entry.

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this change with different models/inputs

Exact local validation:

.venv/bin/python -m pytest tests/unit/clinical/test_evidence_recency.py -q — 10 passed
.venv/bin/python -m pytest tests/unit/test_docs_publication.py::test_publication_classifies_every_default_markdown_page_exactly_once -q — 1 passed
make format — passed; 2036 files unchanged
make lint — passed
make format-check — passed; 2036 files already formatted
make type-check — passed; no issues in 4 configured source files
.venv/bin/mypy --python-version 3.10 openmed/clinical/evidence_recency.py — passed
make docs-build — passed; strict MkDocs and Pages publication validation completed
git diff --cached --check — passed before commit

Checks intentionally not run or awaited:

• The full repository pytest suite (.venv/bin/python -m pytest tests/ -q), per the issue-run validation policy.
• GitHub CI checks; this PR is submitted without waiting for remote checks.
• Swift/OpenMedKit checks; no Swift files changed.
• Model benchmarks and external/network-backed integrations; this feature is standard-library-only and offline.

The docs build emitted existing repository/plugin warnings; it completed
successfully and did not report a documentation error.

Documentation

• I have updated the documentation accordingly
• I have added docstrings to new functions/classes
• I have updated the CHANGELOG.md (not applicable to this issue-scoped v3 feature; no release metadata changed)

Code Quality

• I ran make format, make lint, and make format-check
• For Swift/OpenMedKit changes, I ran make format-swift and make lint-swift
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings (the docs build retains existing repository/plugin warnings)

Dependencies

• I have not added any new dependencies
• OR I have added new dependencies and they are justified because: ____

Checklist

• I have read the contributing guide, Code of Conduct, and maintainer guide
• My commits have clear, descriptive messages
• I have squashed/organized my commits appropriately

Related Issues

Closes #2744

Screenshots/Examples

Not applicable. The documentation includes synthetic Python examples for
single-label classification and value-free reports.