Replace flood-fill scanner with an exact gate template

Instead of guessing a gate's shape by flood-filling connected frame
material, the plugin now matches a fixed ASCII template against the
world (gate.template in config.yml), the same idea as the classic
Stargate plugin's .gate files. Default is an 11x11 ring with 7
chevrons at their real positions rather than auto-spaced.

- New GateTemplate parses the '*'/'1'/'2'/'0' grid.
- New GateTemplateScanner tries every plausible alignment of a
  punched block against a frame/chevron cell, then verifies the rest
  of the template matches; no more flood-fill leak/enclosure
  diagnostics needed since the shape is exact.
- The player's look direction at punch time (snapped to N/S/E/W)
  decides whether template columns run along world X or Z; this
  facing is now stored in Gate.facing (repurposing the old
  sign-attachment field) so restarts can re-scan deterministically.
- Exit-teleport yaw now comes from that stored facing instead of a
  geometric guess.
- Removed gate.chevron-count/max-frame-blocks/max-iris-blocks/
  min-frame-blocks - the template itself defines size and chevrons.

stargate-paper/src/main/resources/config.yml

@@ -26,26 +26,38 @@ cross-server:
   enabled: false
 
 gate:
-  # Any of these materials count as the decorative frame ring. Mix and match to match
-  # your build (the default matches an obsidian/gold-block/birch-planks arch).
+  # The exact shape of a gate, read top row to bottom row. This is matched precisely
+  # against the world - no flood-fill guessing. Symbols:
+  #   * = frame block (never touched by the plugin)
+  #   1 = chevron - a frame block that lights up to chevron-lit-material while
+  #       dialing/open, then reverts to whatever it looked like at rest when closed
+  #   2 = interior ("iris") - filled with iris-material while open, air while closed
+  #   0 = ignored - not part of the gate at all
+  # Must be built in a single vertical plane, one block thick, aligned to the world's
+  # X or Z axis (i.e. facing north/south/east/west, not built at an angle).
+  template:
+    - "00000000000"
+    - "0000*1*0000"
+    - "00012221000"
+    - "00*22222*00"
+    - "0*2222222*0"
+    - "01222222210"
+    - "0*2222222*0"
+    - "00*22222*00"
+    - "00012221000"
+    - "0000***0000"
+    - "00000000000"
+  # Any of these materials satisfy a '*' or '1' cell above. Mix and match to match your
+  # build (the default matches an obsidian/gilded-blackstone ring).
   frame-materials:
     - OBSIDIAN
     - GOLD_BLOCK
     - GILDED_BLACKSTONE
     - BIRCH_PLANKS
     - OAK_PLANKS
-  # Chevrons are NOT a separate material you have to place - the plugin automatically
-  # picks this many frame blocks, evenly spaced around the ring, and swaps them to
-  # chevron-lit-material while dialing/open, then restores whatever they looked like
-  # at rest when the gate closes. So a chevron can rest as plain obsidian and only
-  # stand out once it lights up.
   chevron-lit-material: GILDED_BLACKSTONE
-  chevron-count: 6
   # Material poured into the interior (the "event horizon") while the gate is open.
   iris-material: WATER
-  max-frame-blocks: 300
-  max-iris-blocks: 200
-  min-frame-blocks: 8
   # After placing a "[Stargate]" sign, the owner has this long to left-click (punch) a
   # block of the actual gate frame to link it - the sign itself can sit anywhere, like a
   # DHD console away from the gate, instead of being mounted directly on the frame.