refactor(srp): move urp shadow and prepass core blocks into renderer

docs/used/SRP_URP_RendererCoreShadowPrepassPlan_完成归档_2026-04-21.md

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+# SRP URP Renderer Core Shadow Prepass Plan
+
+Date: 2026-04-21
+
+## Goal
+
+Continue aligning the current managed rendering stack with Unity-style SRP + URP ownership:
+
+- `UniversalRenderer` owns the default shadow and depth-prepass core blocks
+- `ScriptableRendererFeature` injects or explicitly overrides stage existence through planning hooks
+- standalone stage fallback remains secondary instead of being the primary owner of URP core blocks
+
+This stage does not add deferred rendering.
+
+## Current Problems
+
+The current code still has three architectural gaps:
+
+1. `UniversalRenderer` explicitly owns final output, but shadow and depth-prepass core blocks are still not renderer-owned managed defaults.
+2. `ScriptableRenderer.FinalizeCameraFramePlan()` infers standalone stages from the queued pass list without respecting explicit shadow/depth planning decisions, so a feature-level `ClearShadowCasterStage()` can be silently undone later.
+3. `UniversalRendererData` still exposes native standalone pass keys for `ShadowCaster` and `DepthOnly`, so the managed renderer core is not yet the obvious primary ownership seam.
+
+## Scope
+
+### 1. Make shadow / depth stage planning explicit
+
+Required work:
+
+- expose explicit standalone-stage planning state to managed code
+- skip inferred shadow/depth stage requests when the renderer or a feature has already configured those stages explicitly
+- preserve the existing inferred path only for renderers that still rely on implicit standalone-stage discovery
+
+### 2. Move default shadow / depth core passes into `UniversalRenderer`
+
+Required work:
+
+- add default managed `DrawObjectsPass` instances for:
+  - `ShadowCaster`
+  - `DepthOnly`
+- make `UniversalRenderer` decide whether those blocks exist
+- keep shadow stage tied to actual shadow-plan availability
+- keep depth prepass opt-in instead of enabling it unconditionally
+
+### 3. Reduce native fallback ownership in URP data
+
+Required work:
+
+- stop treating native standalone asset keys as the primary URP shadow/depth implementation path
+- make `UniversalRendererData` describe the renderer-owned default blocks instead
+- keep fallback compatibility only where it is still useful during transition
+
+## Out Of Scope
+
+- deferred renderer
+- GBuffer
+- editor-side renderer configuration UX
+- moving every shadow implementation detail out of native code
+- multiple URP renderer variants in this stage
+
+## Done Criteria
+
+1. `UniversalRenderer` owns default managed shadow and depth-prepass block composition.
+2. Feature-level explicit shadow/depth stage planning is no longer overwritten by generic queue inference.
+3. URP shadow/depth defaults no longer depend on `UniversalRendererData.GetCameraFrameStandalonePassAssetKey(...)` as the main ownership seam.
+4. Old `XCEditor` builds in Debug.
+5. Old editor smoke passes for at least about 10 seconds and a fresh `SceneReady` appears in `editor/bin/Debug/editor.log`.
+
+## Follow-Up
+
+After this stage closes, the next SRP stage can move higher toward Unity-style renderer composition:
+
+- renderer variants / multiple renderer assets
+- managed shadow block enrichment
+- managed prepass expansion
+- eventually, SRP-facing C# pipeline composition with clearer URP package layering