Separate out into files

docs/architecture.md

@@ -20,6 +20,28 @@ Pointer movement changes only a CSS progress variable. Built-in presentations re
 
 Settling animations are interruptible. A new button navigation or recognized gesture waits only for any in-flight Vue Router guard/history commit, immediately finalizes the old visual transaction, and begins from the newly authoritative route. It never waits for the previous spring to finish. Leading-edge back recognition runs in the navigator capture phase so partially visible component layers cannot steal the physical back edge.
 
+### Runtime domains
+
+`runtime.ts` is the public transaction coordinator. Its supporting domains live
+under `packages/core/src/runtime`:
+
+- `vue-router-bridge.ts` contains all Vue Router-specific integration: route
+  resolution and loading, commit operations, `afterEach` reconciliation,
+  browser-history completion, and the scoped Options API `$route` bridge.
+- `history-ledger.ts` owns native push, replace, and pop history semantics.
+- `view-store.ts` owns mounted route entries, active state, preview reuse,
+  eviction, underlay protection, and cache statistics.
+- `animation.ts` owns gesture commit policy, view preparation, and spring
+  settling.
+- `presentations.ts` owns built-in and application-defined presentations.
+- `diagnostics.ts` owns runtime diagnostic subscriptions and event emission.
+- `route-entry.ts` owns route-entry construction, labels, timestamps, and
+  sibling direction.
+
+Keeping the Vue Router adapter separate makes the compatibility work visible
+and prevents history, cache, rendering, and animation policy from accumulating
+inside the integration layer.
+
 Component gesture owners stop propagation before a containing navigator can claim the same pointer. Navigator gestures wait for horizontal intent, use pointer capture, respect form controls and `data-native-gesture="ignore"`, and preserve normal vertical scrolling through `touch-action: pan-y`.
 
 ## Route metadata