Finished phase 1

docs/subsystems/RuntimeSnapshotProvider.md

@@ -8,13 +8,13 @@ The goal of `RuntimeSnapshotProvider` is to separate render-facing state publica
 
 `RuntimeSnapshotProvider` is the boundary between runtime-owned state and render-consumable state.
 
-It exists to solve three current problems:
+It exists to solve three problems that Phase 1 pulled apart:
 
-- render state is still built directly out of `RuntimeHost` under a shared mutex
-- render reads and refreshes partially mutable cached layer state in more than one place
+- render state was built directly out of `RuntimeHost` under a shared mutex
+- render read and refreshed partially mutable cached layer state in more than one place
 - state publication, state versioning, and dynamic frame-field refresh need explicit ownership
 
-Today the closest current behavior lives in:
+Before the Phase 1 runtime split, the closest behavior lived in:
 
 - `RuntimeHost::GetLayerRenderStates(...)`
 - `RuntimeHost::TryGetLayerRenderStates(...)`
@@ -340,7 +340,7 @@ This is especially important while migrating away from the current lock/fallback
 
 ## Current Code Mapping
 
-The current code suggests the following migration map.
+The current code follows this migration map.
 
 ### Move into `RenderSnapshotBuilder`
 
@@ -370,12 +370,12 @@ Current methods that should become compatibility shims and later disappear:
 
 The previous `OpenGLComposite` cache path:
 
-- reads versions from `RuntimeHost`/store-owned counters
+- read versions from `RuntimeHost`/store-owned counters
 - conditionally calls `TryRefreshCachedLayerStates(...)`
 - conditionally rebuilds full layer state
 - then reapplies render-local OSC overlay state
 
-During migration, that should become:
+The migrated runtime path is:
 
 1. get latest published snapshot from provider
 2. compare snapshot versions produced by `RenderSnapshotBuilder`
@@ -390,12 +390,12 @@ That is a much cleaner split than the current mixed lock/cache/fallback flow in
 ### Step 1: Introduce provider types without changing behavior
 
 - define `RuntimeRenderSnapshot`, `RuntimeRenderLayerSnapshot`, and `RuntimeRenderFrameContext`
-- implement provider methods as thin wrappers over current `RuntimeHost` logic
-- keep `RuntimeHost` as the backing source temporarily
+- initially implement provider methods as thin wrappers over existing behavior
+- completed: replace the temporary `RuntimeHost` backing source with `RenderSnapshotBuilder`
 
 ### Step 2: Route render reads through the provider
 
-- replace direct `RuntimeHost` layer-state reads with provider snapshot reads
+- replace direct host/store layer-state reads with provider snapshot reads
 - preserve current version behavior first, even if internally bridged to existing counters
 
 ### Step 3: Separate structural publication from frame context
@@ -479,7 +479,7 @@ Recommended tests:
 
 `RuntimeSnapshotProvider` can be considered architecturally in place once:
 
-- render no longer reads `RuntimeStore` or `RuntimeHost` render state directly
+- render no longer reads `RuntimeStore` or legacy host render state directly
 - render consumes published snapshot handles rather than rebuilding layer vectors from host state
 - dynamic frame fields are supplied separately from structural snapshot publication
 - snapshot version domains are explicit and observable
@@ -497,4 +497,4 @@ Its contract is:
 - keep frame-local timing separate
 - give render a cheap, lock-light read path
 
-If that boundary is held, later phases can split `RuntimeHost`, isolate render timing, and decouple playout without inventing a second render-state authority.
+If that boundary is held, later phases can isolate render timing and decouple playout without inventing a second render-state authority.