Check landing spot is actually open space, not just clear of the iris

computeSafeLanding() pushed the arrival point along the entry
direction only until it cleared the destination's iris footprint - it
never checked whether that spot was solid ground. A gate built close
to a wall (e.g. inside a room/temple) could push the landing straight
into that wall, embedding the player in it - which incidentally let
them walk out through the wall instead of a door, since they're
already clipped partway through it.

Now checks feet AND head height at each step for solid blocks while
searching forward (up to 8 blocks), stopping at the first spot that's
both clear of the iris and open space. Falls back to the furthest
wall-clear point found if nothing satisfies both within range, rather
than the original blind offset.

stargate-paper/src/main/java/dev/skywalker3200/stargate/paper/gate/GateManager.java

@@ -491,13 +491,35 @@ public class GateManager {
         if (dir.lengthSquared() < 0.0001) dir = new Vector(0, 0, 1);
         dir.normalize();
 
-        for (int i = 0; i < 8 && !irisXZ.isEmpty(); i++) {
-            long key = ((long) Math.floor(x) << 32) ^ ((long) Math.floor(z) & 0xFFFFFFFFL);
-            if (!irisXZ.contains(key)) break;
+        // Push clear of the iris footprint (so arrival doesn't immediately re-trigger the
+        // teleport) AND clear of any solid block at foot/head height - a wall close behind the
+        // gate (e.g. built inside a room) can otherwise land the player embedded in it. Falls
+        // back to the furthest wall-clear spot found if nothing satisfies both within range.
+        double lastClearX = x, lastClearZ = z;
+        boolean foundClear = false;
+        for (int i = 0; i <= 16; i++) {
+            boolean inIris = irisXZ.contains(((long) Math.floor(x) << 32) ^ ((long) Math.floor(z) & 0xFFFFFFFFL));
+            Block feet = world.getBlockAt((int) Math.floor(x), (int) Math.floor(y), (int) Math.floor(z));
+            Block head = feet.getRelative(0, 1, 0);
+            boolean solid = feet.getType().isSolid() || head.getType().isSolid();
+
+            if (!inIris && !solid) {
+                foundClear = true;
+                break;
+            }
+            if (!solid) {
+                lastClearX = x;
+                lastClearZ = z;
+            }
             x += dir.getX() * 0.5;
             z += dir.getZ() * 0.5;
         }
 
+        if (!foundClear) {
+            x = lastClearX;
+            z = lastClearZ;
+        }
+
         return new Location(world, x, y, z, yaw, pitch);
     }
 }