feat: Add client gametest for tank rendering verification

[turtton]

Summary

• Fabric のクライアントゲームテスト機能を使い、タンク描画のスクリーンショットベース検証テストを追加
• clientGametest ソースセットを手動作成し、サーバー側 gametest と分離
• CI に client-game-test ジョブを追加（スクリーンショットをアーティファクトとして保存）

テストケース

1. 空のタンク単体
2. 水で満タンのタンク (fillLevel = 1.0)
3. 水が半分のタンク (fillLevel ≈ 0.5)
4. 水平連結タンク（横 2 つ並び）
5. 縦積みタンク（縦 2 つ）

その他の変更

• CTBlocks.syncGroupBlockEntities の可視性を internal → public に変更（テストモジュールからのアクセスに必要）
• .gitignore に /net/ を追加（Loom デコンパイルソース除外）

Test plan

• ./gradlew build 通過
• ./gradlew spotlessCheck 通過
• ./gradlew runClientGameTest でスクリーンショットが build/run/clientGameTest/screenshots/ に生成されることを確認
• CI の client-game-test ジョブが成功し、スクリーンショットがアーティファクトにアップロードされることを確認

[Copilot]

Pull request overview

Adds Fabric client-side GameTest coverage to verify ConnectedTank rendering via screenshot capture, separating client tests into a dedicated clientGametest source set and wiring CI to run the client test task and upload screenshots as artifacts.

Changes:

• Introduces a new clientGametest source set + Loom run configurations for client GameTests.
• Adds a client GameTest mod (connectedtank-client-test) with screenshot-based rendering scenarios.
• Updates CI to run the production client GameTest task and upload generated screenshots.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/main/kotlin/net/turtton/connectedtank/block/CTBlocks.kt	Makes syncGroupBlockEntities callable from the client test module.
src/clientGametest/resources/fabric.mod.json	Declares a separate client-only test mod and entrypoint for Fabric client GameTests.
src/clientGametest/kotlin/net/turtton/connectedtank/test/ConnectedTankClientGameTest.kt	Implements screenshot capture scenarios for tank rendering verification.
build.gradle.kts	Adds clientGametest source set, Loom run(s), and production client test task.
.gitignore	Ignores Loom decompiled sources directory at repo root.
.github/workflows/build.yml	Adds client-game-test CI job to run client GameTests and upload screenshots.

Comments suppressed due to low confidence (1)

src/main/kotlin/net/turtton/connectedtank/block/CTBlocks.kt:46

• syncGroupBlockEntities was changed from internal to public. Since this is effectively an internal sync helper (it mutates client-render-facing block entities from server state), consider marking it explicitly as non-API (e.g., with an internal-use annotation / visibility wrapper) to avoid accidentally committing to it as part of the mod’s public API surface while still allowing test access.

    fun syncGroupBlockEntities(
        world: ServerWorld,
        pos: BlockPos,
        state: FluidStoragePersistentState = world.persistentStateManager.getOrCreate(FluidStoragePersistentState.TYPE),
    ) {

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[Copilot]

TANK_CAPACITY is a regular val but is named like a compile-time constant (all-caps with underscores). To match Kotlin naming conventions and avoid implying const val semantics, rename this to lowerCamelCase (or make it a const val if you can express it as a compile-time constant).

Suggested change

	private val TANK_CAPACITY = CTServerConfig.DEFAULT_BUCKET_CAPACITY.toLong()
	private val tankCapacity = CTServerConfig.DEFAULT_BUCKET_CAPACITY.toLong()

[Copilot]

This workflow runs a Minecraft client task on ubuntu-24.04 without setting up an X/GL context (e.g., via xvfb-run). On GitHub-hosted Linux runners, GUI/OpenGL apps typically fail with missing DISPLAY/GL errors unless wrapped in Xvfb (and sometimes mesa libs). Consider running the Gradle command under xvfb-run -a (and installing any required packages) to make the CI job reliable.

Suggested change

	- name: Run client game tests
	run: ./gradlew runProductionClientGameTest
	- name: Install Xvfb and Mesa
	run: |
	sudo apt-get update
	sudo apt-get install -y xvfb mesa-utils
	- name: Run client game tests
	run: xvfb-run -a ./gradlew runProductionClientGameTest