feat: overhaul movement for flow — momentum-preserving states, smooth crouch, landing feel

- Quake-style air-strafe accelerate (real speed gain from strafing; external
  speed from dash/rockets never clamped)
- Wall run: keeps entry momentum (incl. upward carry), accelerates along the
  wall instead of hard-setting velocity, gravity fades in over the run
- Slide: slope physics (gravity projected along floor accelerates downhill),
  flat-ground decel instead of multiplicative friction, entry boost, direct
  slide->wallrun and slide->dash transitions
- Dash: cooldown 10s -> 2s, per-player (was a static shared across instances),
  momentum fully kept on exit, FOV punch event
- Grapple: taut pendulum with active rope control (W reels in, S pays out),
  release keeps swing energy
- Wall climb: carries upward momentum in, jump-off kick, shared vault helper
- Crouch capsule: single owner in the machine, smoothly lerped, ceiling check;
  camera eye height follows via crouch factor (no more head snapping)
- Landing: machine emits 'land' events scaled by impact; camera dip + pitched
  down thud; footsteps get pitch variation
- Camera rig: event-driven (land dip, dash FOV kick, vault pitch impulse),
  slide roll tilt
- Model: Jump vs Fall split by vertical velocity, Land one-shot on heavy
  landings, wall-run body lean (synced to remotes via synced_wall_side)

Co-Authored-By: Claude Fable 5 <[email protected]>

scenes/maps/procedural_arena/procedural_arena_runtime.gd

@@ -82,6 +82,7 @@ func _spawn_player(pid: int) -> CharacterBody3D:
 	client_rep_config.add_property(":synced_movement_speed")
 	client_rep_config.add_property(":synced_is_crouching")
 	client_rep_config.add_property(":synced_is_ads")
+	client_rep_config.add_property(":synced_wall_side")
 	client_rep_config.add_property(":synced_grapple_point")
 	client_rep_config.add_property(":synced_is_grapple_shooting")
 	client_rep_config.add_property(":synced_skin_id")