v2.7.2: Outcome rendering and filter-disclosure correctness

Outcome rendering and filter-disclosure correctness

Corrects misleading output across five tools: not-reached arms no longer vanish from outcome summaries, truncation and cap flags fire only on real overflow, and an empty field list is rejected instead of dumping the full catalog.

Changed:

• get_study_count echoes sentinelFilterActive: true when the default unknown-enrollment exclusion is in effect, matching search_studies (#78)
• get_study_record filtersApplied records a cap and its upstream total only when the cap actually trimmed the set; nearLocation still always echoes (#80)
• get_study_record nearLocation notes that distanceMi reflects city-centroid geocoding granularity, not facility-level (#81)

Fixed:

• get_study_results retains NA/NR (median not reached) outcome arms, rendering them as "not reached" for MEDIAN measures instead of dropping the arm (#76)
• get_field_definitions sets the search truncated flag only when matches exceed the cap (searchFields returns the pre-cap total) (#77)
• get_field_values rejects an empty fields list with a field_invalid error instead of returning the full ~418-field catalog (#82)

524 tests pass; bun run devcheck clean.