NS-23: allow ground pick on bump slopes (fix stuck departure)

MIN_WALKABLE_NORMAL_DOT_UP 0.82 is stricter than NS-19 frustum slopes
(~45° / dot 0.71 on Bump A, ~39° / 0.78 on B). Clicks off the plateau
often hit the slope first; the pick was dropped with no MoveCommand.
Lower to 0.64 so ramps register; vertical walls remain ~0.

client/scripts/ground_pick.gd

@@ -1,14 +1,14 @@
 extends Node3D
 
 ## NS-16: walkable ground ray pick. Emits world target for MoveCommand; camera wired from main.
-## NS-19: ignores hits on **steep** surfaces (e.g. pedestal **walls**) so players cannot chain small
-## vertical steps up a vertical face; only **floor-like** normals (high dot with UP) count.
+## NS-19: reject vertical faces (pedestal). Bump slopes ~39–45° (dot UP ~0.71–0.78).
+## 0.82 rejected slope-first picks when leaving plateau; use 0.64. Walls stay ~0.
 ## (No `class_name` so headless/CI can load the project before `.godot` import exists.)
 
 signal target_chosen(world: Vector3)
 
 ## Minimum `hit_normal.dot(Vector3.UP)` to accept a pick (0 = vertical wall, 1 = flat floor).
-const MIN_WALKABLE_NORMAL_DOT_UP: float = 0.82
+const MIN_WALKABLE_NORMAL_DOT_UP: float = 0.64
 
 ## Fallback when `Viewport.get_camera_3d()` is null (e.g. some editor setups). Set from `main.gd`
 ## in `_ready`.