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.

README.md

@@ -16,29 +16,52 @@ Build everything with `./gradlew build`. Jars land in each module's `build/libs/
 
 ## Building a gate
 
-1. Build a fully-enclosed ring out of any block(s) in `gate.frame-materials` (default:
-   obsidian, gold block, gilded blackstone, birch/oak planks). Leave the middle hollow.
-   No gaps - the ring must be a sealed loop.
-2. Nothing else to build for chevrons. On creation, the plugin automatically picks
-   `gate.chevron-count` (default 6) frame blocks, evenly spaced around the ring, and
-   remembers what they looked like at rest. While dialing/open those blocks swap to
-   `gate.chevron-lit-material` (default gilded blackstone); closing the gate restores
-   them to their original block, so a chevron can rest as plain obsidian and blend
-   invisibly into the frame until it lights up.
-3. Place a sign anywhere - it doesn't need to touch the frame, so it can act like a DHD
+A gate's shape is a fixed template in `config.yml` (`gate.template`), matched exactly
+against the world - not flood-filled or guessed. The default is an 11x11 ring with 7
+chevrons, laid out top row to bottom row:
+
+```
+00000000000
+0000*1*0000
+00012221000
+00*22222*00
+0*2222222*0
+01222222210
+0*2222222*0
+00*22222*00
+00012221000
+0000***0000
+00000000000
+```
+
+- `*` — frame block, never touched by the plugin. Must be one of `gate.frame-materials`
+  (default: obsidian, gold block, gilded blackstone, birch/oak planks).
+- `1` — a chevron: a frame block (same material rules as `*`) that swaps to
+  `gate.chevron-lit-material` (default gilded blackstone) while dialing/open, then
+  reverts to whatever it looked like at rest when the gate closes. So a chevron can
+  rest as plain obsidian and blend invisibly into the frame until it lights up.
+- `2` — interior ("iris"), filled with `gate.iris-material` (default water) while open.
+- `0` — ignored, not part of the gate.
+
+Build it in a single vertical plane, one block thick, aligned to the world's X or Z
+axis (facing north/south/east/west - not built at an angle). Edit `gate.template` in
+`config.yml` if you want a different size or chevron count/placement.
+
+1. Build the frame to match the template.
+2. Place a sign anywhere - it doesn't need to touch the frame, so it can act like a DHD
    console standing apart from the gate - with:
    - Line 1: `[Stargate]`
    - Line 2: network name (blank = default network)
    - Line 3: gate name (blank = auto-generated)
    - Line 4: `hidden` to keep it out of the cycle list, `fixed:GateName` to lock this
      gate to always dial `GateName` (no right-click cycling), or blank
-4. The sign will show "Punch the gate (30s)". Within `gate.link-timeout-seconds`,
-   left-click (punch) any block of the frame ring, within `gate.max-link-distance` of
-   the sign. The plugin flood-fills out from that block, confirms it's a fully enclosed
-   ring, and links the sign to it.
+3. The sign will show "Punch the gate (30s)". Within `gate.link-timeout-seconds`, stand
+   facing the gate square-on and left-click (punch) any `*` or `1` block, within
+   `gate.max-link-distance` of the sign. The plugin matches the template against the
+   world starting from that block and links the sign to it.
 
-If punching a block doesn't work, the plugin tells you exactly why in chat - an
-unrecognized frame material, a gap in the ring, too far from the sign, etc.
+If punching a block doesn't work, the plugin tells you exactly why in chat - wrong
+material, no orientation of the template lines up, too far from the sign, etc.
 
 ## Using a gate