feat: improve heuristic table detection for small body-font tables

- Lower minimum item count for body-font table candidates from 9 to 6,
  allowing small 2-3 row tables to be detected.
- Allow 2-column body-font tables with short cells (avg ≤25 chars) to
  bypass the "table-like content" validation. This catches text-only
  definition/category tables (e.g., species lists) without false-positiving
  on 2-column paragraph text (which has longer cells).

Benchmark improvement: TEDS 0.498→0.519, overall 0.750→0.754.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/snapshots/thermo-freon12.md

@@ -26,19 +26,16 @@ S = Entropy (kJ/kg.K)
 
 **Physical Properties**
 
-Chemical Formula CCl2F2
+|Chemical Formula|CCl2F2|
+|---|---|
+|Molecular mass|120.91|
+|Boiling Point At one atmosphere|-29.75°C|
+|Critical Temperature|111.97°C|
+|Critical Pressure|4136 kPa|
+|Critical Density|565.0 kg/m|
+|Critical Volume|0.0018 m|
 
-Molecular mass 120.91
-
-Boiling Point-29.75°C At one atmosphere
-
-Critical Temperature 111.97°C
-
-Critical Pressure 4136 kPa
-
-3 Critical Density 565.0 kg/m
-
-Critical Volume 0.0018 m /kg
+/kg
 
 l