feat(packages): ludic.character - a third-person walking body: walk and run with their acceleration, a jump and gravity, a step within CHAR_STEP taken and a slope above it measured over a fixed probe, wading that shelves into a swim, the dive and the breath, sitting, one safe put-down spot, holds by reason, being carried, and the orbit camera with first-person eyes; ground, body and stick through ports; landed, jumped, footfall, too steep, the water's facts

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.character/sit.ludic

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+# sit.ludic - sitting: on a seat's point, or on the ground where the body stands. The pose either
+# side is a still one, so the sit's own weight (body_sit_t) eases 0 -> 1 over a quarter second and
+# the body walks the last step to the seat over the same time rather than jumping there.
+export function char_sit(x: float, z: float, yaw: float, mode: int) -> void {
+  chr_sit = true
+  chr_sit_mode = mode
+  chr_speed = 0.0
+  chr_move = 0.0
+  chr_run = 0.0
+  chr_sit_x = x
+  chr_sit_z = z
+  chr_sit_yaw = yaw
+  chr_water = CharacterGround.water(chr_x, chr_z)
+}
+
+function chr_sit_tick(dt: float) -> void {
+  var want = 0.0
+  if chr_sit { want = 1.0 }
+  chr_sit_t = char_toward(chr_sit_t, want, 4.0 * dt)
+  if not chr_sit { return }
+  let k = Math.min(1.0, 8.0 * dt)
+  chr_x = Math.lerp(chr_x, chr_sit_x, k)
+  chr_z = Math.lerp(chr_z, chr_sit_z, k)
+  chr_yaw = chr_yaw + char_wrap(chr_sit_yaw - chr_yaw) * k
+  chr_y = CharacterGround.height(chr_x, chr_z)
+  chr_water = CharacterGround.water(chr_x, chr_z)
+}
+
+# Sitting down where the body stands: not astride something, not in the air, not on a slope,
+# not in the water. Asked again while sitting, it stands up. The answer is a CHAR_* for the game
+# to word.
+export function char_sit_here() -> int {
+  if chr_sit {
+    char_stand()
+    return CHAR_STOOD
+  }
+  if CharacterBody.riding() { return CHAR_NOT_RIDING }
+  if chr_air { return CHAR_NOT_AIRBORNE }
+  if CharacterGround.slope(chr_x, chr_z) > 0.35 { return CHAR_NOT_STEEP }
+  if chr_y < chr_water + 0.9 { return CHAR_NOT_WET }
+  char_sit(chr_x, chr_z, chr_yaw, CHAR_SIT_GROUND)
+  return CHAR_SAT
+}
+
+# standing up out of a seat put down against a boulder or a bank must not leave the body inside it
+export function char_stand() -> void {
+  chr_sit = false
+  if char_safe_spot(chr_x, chr_z, chr_y, 0.0) {
+    chr_x = chr_safe_x
+    chr_z = chr_safe_z
+    chr_y = CharacterGround.height(chr_x, chr_z)
+  }
+}
+
+# smoothstep, so a pose slows into the seat rather than arriving at full speed
+export function char_ease(t: float) -> float {
+  let c = Math.clamp(t, 0.0, 1.0)
+  return c * c * (3.0 - 2.0 * c)
+}