Add section-aware grounding context that scopes concept matches by note section #929

Summary

The same term grounds differently by section (a drug under 'Allergies' is an allergen, under 'Medications' an active drug, under 'Family History' not the patient's). A grounding-context layer that biases and constrains candidate concepts by the detected section materially improves grounding precision.

Scope

• Add clinical/grounding/section_context.py mapping detected sections to semantic-type biases and exclusions for grounding
• Adjust ConceptMatch ranking and filter implausible concepts given the section (e.g. allergen vs medication)
• Attach the governing section and any experiencer to each grounded concept for downstream filtering
• Expose apply_section_context(matches, sections, experiencer)

Acceptance criteria

• Golden fixture grounds the same term to different/biased concepts under Allergies vs Medications sections
• Family-history-section concepts are tagged non-patient and down-ranked for the patient record
• Section biases are data-driven and configurable, not hard-coded constants
• Offline; no raw PHI persisted beyond offsets and concept ids

Out of scope

• The clinical section detector itself (already shipped/wired)
• Concept-normalization confidence calibration (separate task)

Files

• openmed/clinical/grounding/section_context.py
• tests/unit/clinical/grounding/test_section_context.py

Task: OM-572 · Milestone: v2.2 · Priority: P2 · Size: M
Depends on: OM-510 · Blocks: —
Roadmap: v2.2 trustworthy clinical data exchange follow-on wave
Spec: PLANS/V2/EXECUTION/tasks/OM-572.md