feat(packages): ludic.compass - bearing marks on a strip: marks gathered once a frame from an open registry of providers (CompassProviders), gated by the viewer's tier, sorted tracked / note / plain and culled to a cap; bearings and distances off the viewer's facing, the tracked mark, a capture that lets a guide hear the providers whatever the tier, the eight points, and the radar's range per tier with blips on a unit disc; the viewer through a port

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

packages/ludic.compass/gather.ludic

@@ -0,0 +1,56 @@
+# gather.ludic - a frame's marks: begin, every provider marks, end sorts and culls. While a
+# capture is open the marks go to whoever is listening instead, whatever the tier.
+export function compass_begin() -> void { cmp_list = new []CompassMark }
+
+# a provider's verb: a thing at (x, z), shown from compass `tier` up
+export function compass_mark(x: float, z: float, icon: int, colour: int, tier: int, prio: int, label: string) -> void {
+  if cmp_list == null { compass_begin() }
+  let m = cmp_new(x, z, icon, colour, tier, prio, label)
+  if cmp_capturing {
+    push(cmp_caught, m)
+    return
+  }
+  if CompassWorld.tier() < tier { return }
+  push(cmp_list, m)
+}
+
+# highest priority first, the providers' order kept within one; then the cap
+export function compass_end() -> void {
+  if cmp_list == null { compass_begin() }
+  let out = new []CompassMark
+  for p in 0 .. 3 {
+    let want = COMPASS_TRACKED - p
+    for i in 0 .. len(cmp_list) { if cmp_band(cmp_list[i].prio) == want and len(out) < cmp_cap { push(out, cmp_list[i]) } }
+  }
+  cmp_list = out
+}
+
+function cmp_band(p: int) -> int { return Math.clamp(p, COMPASS_PLAIN, COMPASS_TRACKED) }
+
+# once a frame: ask every registered provider, in the registry's order
+export function compass_gather() -> void {
+  compass_begin()
+  if CompassWorld.tier() <= 0 { return }
+  for i in 0 .. COMPASS_FROM_COUNT {
+    let f = CompassProviders[i].gather
+    if f != null { f() }
+  }
+  compass_end()
+}
+
+# someone else wants to know where the providers point (a guide's arrow): until the end every
+# mark is theirs, whatever the tier, and the frame's list is left alone
+export function compass_capture_begin() -> void {
+  cmp_capturing = true
+  cmp_caught = new []CompassMark
+}
+
+export function compass_capture_end() -> []CompassMark {
+  cmp_capturing = false
+  var got = cmp_caught
+  cmp_caught = new []CompassMark
+  if got == null { got = new []CompassMark }
+  return got
+}
+
+export function compass_capturing() -> bool { return cmp_capturing }