feat(rendering): add transparent object support for reflection probe

[xubing0906]

Re: cocos/cocos-engine#16297

Summary

• Add supportTransparency option to ReflectionProbe component (CUBE mode)
• When enabled, use RGBA16F intermediate RT for correct alpha blending, then convert to RGBE via a fullscreen pass
• Support both Custom/Builtin pipeline and Legacy ForwardPipeline
• Add CC_USE_FLOAT_PROBE_OUTPUT shader macro to skip RGBE encoding and tone mapping in float probe path

Changes

• Component/render-scene layer: supportTransparency property, useFloatIntermediateRT(), RGBA16F intermediate texture lifecycle
• Custom pipeline: float RT resource allocation, probe convert pass (_buildProbeConvertPass), transparent queue (SceneFlags.BLEND) for probe rendering
• Legacy pipeline: _renderConvertPass fullscreen quad in ReflectionProbeStage, transparent object collection in RenderReflectionProbeQueue
• Shaders: CC_USE_FLOAT_PROBE_OUTPUT branch in 5 chunk files + skybox effect; new probe-rgbe-convert.effect (technique 0 for Custom, technique 1 for Legacy)

Test plan

• Enable supportTransparency on a CUBE probe, verify transparent objects appear in reflection
• Disable supportTransparency, verify behavior unchanged (transparent objects excluded, RGBE encoding direct)
• Test Planar probe with transparency enabled
• Test both Custom pipeline and Legacy ForwardPipeline
• Verify no regression on existing opaque-only reflection probes

---

Continuous Integration

This pull request:

• needs automatic test cases check.

  Manual trigger with @cocos-robot run test cases afterward.

• does not change any runtime related code or build configuration

  If any reviewer thinks the CI checks are needed, please uncheck this option, then close and reopen the issue.

---

Compatibility Check

This pull request:

• changes public API, and have ensured backward compatibility with deprecated features.
• affects platform compatibility, e.g. system version, browser version, platform sdk version, platform toolchain, language version, hardware compatibility etc.
• affects file structure of the build package or build configuration which requires user project upgrade.
• introduces breaking changes, please list all changes, affected features and the scope of violation.

[github-actions]

Code Size Check Report

Wechat (WASM)	Before	After	Diff
2D Empty (legacy pipeline)	1015290 bytes	1018570 bytes	⚠️ +3280 bytes
2D All (legacy pipeline)	2683021 bytes	2686313 bytes	⚠️ +3292 bytes
2D All (new pipeline)	2774976 bytes	2776493 bytes	⚠️ +1517 bytes
(2D + 3D) All	10032418 bytes	10036591 bytes	⚠️ +4173 bytes

Web (WASM + ASMJS)	Before	After	Diff
(2D + 3D) All	16868836 bytes	16873012 bytes	⚠️ +4176 bytes

Interface Check Report

! WARNING this pull request has changed these public interfaces:

@@ -5639,8 +5639,16 @@
          * @zh 快速烘焙不会进行卷积。
          */
         get fastBake(): boolean;
         set fastBake(val: boolean);
+        /**
+         * @en Whether to support transparent objects in reflection probe rendering.
+         * When enabled, uses RGBA16F intermediate RT for correct alpha blending.
+         * @zh 是否支持半透明物体参与反射探针渲染。
+         * 开启后使用 RGBA16F 中间 RT 以支持正确的 alpha 混合。
+         */
+        get supportTransparency(): boolean;
+        set supportTransparency(val: boolean);
         set cubemap(val: TextureCube | null);
         get cubemap(): TextureCube | null;
         get probe(): renderer.scene.ReflectionProbe;
         /**
@@ -45497,9 +45505,9 @@
          * @zh 设置probe信息
          * @param probe
          * @param frameBuffer
          */
-        setUsageInfo(probe: renderer.scene.ReflectionProbe, frameBuffer: gfx.Framebuffer, reflectionCamera?: renderer.scene.Camera): void;
+        setUsageInfo(probe: renderer.scene.ReflectionProbe, frameBuffer: gfx.Framebuffer, outputFrameBuffer?: gfx.Framebuffer | null, reflectionCamera?: renderer.scene.Camera): void;
         destroy(): void;
         clearFramebuffer(camera: renderer.scene.Camera): void;
         render(camera: renderer.scene.Camera): void;
         activate(pipeline: ForwardPipeline, flow: ReflectionProbeFlow): void;

[xubing0906]

@cocos-robot run test cases

[github-actions]

@xubing0906, Please check the result of run test cases:

• Test Platform: PR-Test
• Editor Version: v4.0.0
• Task Result: FAIL
• Task URL: https://cctest.cocos.org/#/reportview/PR-TEST/f34154b0-ff94-4e9c-8838-0beb59c31f8d/-1
• GitHub Action: https://github.com/cocos/cocos4/actions/runs/31143125452

Task Details

Platform	build	boot	runned	crashScene	FailScene
web-mobile	PASS	PASS	FAIL
ios	PASS	PASS	PASS
mac	PASS	PASS	PASS

[github-actions]

@xubing0906, Please check the result of run test cases:

• Test Platform: PR-Test
• Editor Version: v4.0.0
• Task Result: FAIL
• Task URL: https://cctest.cocos.org/#/reportview/PR-TEST/88319a6b-0272-404a-98c6-eb03a0a78b88/-1
• GitHub Action: https://github.com/cocos/cocos4/actions/runs/31143125452

Task Details

Platform	build	boot	runned	crashScene	FailScene
windows	PASS	PASS	PASS
android	PASS	PASS	PASS
wechatgame	PASS	FAIL	FAIL