M2-M8: renderer, playback backends, GUI/network, commands, multi-version build

- M2: VideoAnchorRenderer draws width\u00d7height quad oriented by facing
- M3: VideoBackend interface + JavaCV (reflection) and WaterMedia (probe) backends
- M4: VideoConfigScreen GUI + 4 typed payloads + NBT persistence via ReadView/WriteView
- M5: stick item useOnBlock place/edit, AttackBlockCallback delete, /videoPlace /videoDelete /videoMute
- M6: per-tick distance attenuation gain = volume * clamp(1 - d/16, 0, 1), mute zeroes gain
- M7: WatermediaProbe (reflection-only; reports unavailable until v2 supports 1.21.6+)
- M8: multi-version build script (1.21.6/1.21.7/1.21.8) + Gitea Actions matrix workflow

build.gradle

@@ -26,9 +26,15 @@ dependencies {
 processResources {
     inputs.property "version", project.version
     inputs.property "mod_id", project.mod_id
+    inputs.property "minecraft_version", project.minecraft_version
+
+    // Pin the fabric.mod.json's minecraft constraint to the build's exact target — keeps each
+    // multi-version jar from claiming compatibility it doesn't have.
+    def mc = project.minecraft_version
+    def target = "~${mc}"
 
     filesMatching("fabric.mod.json") {
-        expand "version": project.version, "mod_id": project.mod_id
+        expand "version": project.version, "mod_id": project.mod_id, "target_minecraft": target
     }
 }