docs: fix N2 STP-to-liquid constant in README table

Author: Hj1308

CHANGELOG.md

@@ -26,6 +26,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `--no-show` disabled saving instead of display.
 - Hysteresis scoring double-counted `is_flat_low`; score ties were resolved by
   dict insertion order.
+- Documentation: the README "Physical Constants" table listed the STP→liquid
+  factor as `N2_LIQUID_FACTOR = 1547.0` — a name that never existed in the
+  code, and a value 2.393× too high. Renamed to `N2_STP_TO_LIQUID = 1.5468e-3`
+  to match `bet_analysis.py`; the Gurvich computation itself has been correct
+  since v3.0.0.
 
 ### Added
 

README.md

@@ -199,7 +199,7 @@ All constants are defined as named variables at the top of `bet_analysis.py` (no
 |----------|-------|------------|
 | `N2_BET_FACTOR` | 4.353 m² g⁻¹ per cm³(STP) g⁻¹ | N₂ cross-section σ = 0.162 nm², Avogadro + molar volume |
 | `N2_TPLOT_SLOPE_FACTOR` | 15.47 m² g⁻¹ per cm³/(g·Å) | Harkins-Jura t-curve conversion |
-| `N2_LIQUID_FACTOR` | 1547.0 cm³(STP) per cm³(liquid N₂) | At 77 K |
+| `N2_STP_TO_LIQUID` | 1.5468e-3 cm³(liquid N₂) per cm³(STP) | Gurvich rule: V_liquid = V_STP × N2_STP_TO_LIQUID (77 K) |
 | `N2_CAVITATION_NM` | 3.4 nm | Forced closure diameter for N₂ at 77 K |
 
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