Revert to flexible flood-fill scanning with geometric chevron placement

The exact-template approach from the last commit over-fit to the
sample ASCII diagram, which was meant to teach the target shape, not
be matched literally cell-for-cell. Back to flood-filling any
connected, fully-enclosed ring the builder makes (any size/shape), but
chevrons are no longer evenly spaced by scan order - the scanner walks
the ring in geometric order and marks local maxima of distance from
the interior's centroid, i.e. the blocks that stick out further than
their ring-neighbours. That's where a real Stargate's chevrons sit
(the 11-wide reference ring naturally produces 7 this way: the top
apex, four shoulder elbows, two side bumps), without hardcoding a
specific size.

Falls back to the old evenly-spaced picker only if the ring isn't a
simple single-thickness loop (each frame block should have exactly
two in-plane neighbours) so odd/thick builds still work.

gate.max-frame-blocks/max-iris-blocks/min-frame-blocks are back;
gate.template is gone.

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

@@ -26,38 +26,29 @@ cross-server:
   enabled: false
 
 gate:
-  # 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).
+  # Any of these materials count as the ring's frame (and count as a valid chevron
+  # material too, since chevrons are just frame blocks the plugin temporarily swaps).
+  # Mix and match to match your build (the default matches an obsidian/gilded-blackstone
+  # ring). The ring can be any size or shape, as long as it's a single connected loop
+  # made only of these materials with a fully sealed hollow interior - no fixed template
+  # or size is required.
   frame-materials:
     - OBSIDIAN
     - GOLD_BLOCK
     - GILDED_BLACKSTONE
     - BIRCH_PLANKS
     - OAK_PLANKS
+  # Chevrons aren't a separate material you place. The plugin flood-fills the ring,
+  # walks it in geometric order, and picks out the blocks that stick further outward
+  # than their ring-neighbours - the "elbow" points of the shape, same as a real
+  # Stargate's chevron placement - then swaps just those to chevron-lit-material while
+  # dialing/open, restoring whatever they looked like at rest when the gate closes.
   chevron-lit-material: GILDED_BLACKSTONE
   # 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.