Set GPS momentum default to 80

docs/compaction-handoff.md

@@ -2,6 +2,26 @@
 
 Current date/time context: 2026-06-27, local timezone America/Chicago.
 
+## 2026-06-27 Momentum Default Chosen
+
+- After live A/B testing and two drive validations, `80.0` is the working
+  default for `momentum_weights.bin`.
+- Source fallback was changed to
+  `kGpsMomentumFixedEdgePenaltyDefault = 80.0f`.
+- `tools/write_momentum_weights.py default` now writes `80.0`.
+  The old `8.0` value is preserved as `legacy-default`.
+- Current preset meanings:
+  `vanilla=0.0`, `mild=4.0`, `legacy-default=8.0`, `strong=16.0`,
+  `default=80.0`, `silly=80.0`, `overstrong=160.0`,
+  `pathological=250.0`.
+- `160.0` was tested and is too high: The Damned can fall back to a straight
+  line, and local access can develop bad hairpins/backtracking.
+- Drive validation at `80.0`:
+  The Damned/Dogtown route drove cleanly at high speed, live minimap
+  recalculation worked after a detour, and the Claire route drove cleanly aside
+  from a driver-unfamiliarity ramp/hill surprise.
+- Updated detailed notes in `docs/gps-momentum-field-tests.md`.
+
 ## 2026-06-27 Live Momentum Knob Installed
 
 - Installed a new telemetry/control DLL at about `03:21` local while the game was