feat(packages): ludic.aim - what the crosshair is on: a ray through the middle of the screen against upright cylinders widened by a fixed angular forgiveness, the nearest one the ground does not hide, reach floored at three metres, and which thing the use key means (that, nothing and say why, or the nearest); the probe of the ground's own answer against the aim; the camera, the ground and the body through a port

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

packages/ludic.aim/pick.ludic

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+# pick.ludic - one target a frame: the game offers every candidate, and the nearest one the ray enters
+# that the ground does not hide is the pick. Near things occlude far ones for free, which is what a
+# player means by "I am looking at that one".
+export const AIM_NONE: int = 0
+export const AIM_REACH_MIN: float = 3.0     # about as far as a hand goes with a step into it
+export const AIM_USE_MAX: float = 10.0      # past this the crosshair is for looking, not doing
+export const AIM_NEVER: float = -1.0        # a reach that is never in reach (an animal without a camera)
+
+var am_kind: int = 0
+var am_id: int = -1
+var am_t: float = 10000.0
+var am_dist: float = 0.0
+var am_reach: bool = false
+var am_off: float = 1.0
+
+# The crosshair decides WHICH; the distance decides only WHETHER. Every reach is lifted to a floor of
+# AIM_REACH_MIN, because a per-kind reach chosen against its model was never chosen against standing
+# between two props and looking at one.
+export function aim_reach_of(reach: float) -> float { return Math.max(reach, AIM_REACH_MIN) }
+
+export function aim_begin() -> void {
+  am_kind = AIM_NONE
+  am_id = -1
+  am_t = 10000.0
+  am_dist = 0.0
+  am_reach = false
+  am_off = 1.0
+}
+
+# A candidate of `kind` (the game's own, not AIM_NONE) and `id`: an upright cylinder at (x, z) from y0
+# to y1 of radius r, within `far` of the body, in reach within `reach` (floored; AIM_NEVER never).
+# True when it is now the pick.
+export function aim_offer(kind: int, id: int, x: float, y0: float, y1: float, z: float, r: float, reach: float, far: float) -> bool {
+  let d = aim_range(x, z)
+  if d > far { return false }
+  let rr = r + aim_slack_m(d)
+  let hit = aim_ray_cyl(x, y0, y1, z, rr)
+  if hit < 0.0 or not (hit < am_t) { return false }
+  if not aim_clear_to(x, (y0 + y1) * 0.5, z) { return false }
+  am_t = hit
+  am_off = aim_miss(x, z, rr)
+  am_kind = kind
+  am_id = id
+  am_dist = d
+  am_reach = reach >= 0.0 and d < aim_reach_of(reach)
+  return true
+}
+
+export function aim_kind() -> int { return am_kind }
+export function aim_id() -> int { return am_id }
+export function aim_dist() -> float { return am_dist }
+export function aim_in_reach() -> bool { return am_reach }
+export function aim_t() -> float { return am_t }
+# how well centred the pick is: 0 dead centre, 1 at its (forgiven) edge
+export function aim_off_centre() -> float { return am_off }