fix(extensions): repair matrix contracts and test boundaries

extensions/matrix/src/channel.ts

@@ -434,7 +434,7 @@ export const matrixPlugin: ChannelPlugin<ResolvedMatrixAccount> = {
       //
       // INVARIANT: The import() below cannot hang because:
       // 1. It only loads local ESM modules with no circular awaits
-      // 2. Module initialization is synchronous (no top-level await in ./matrix/index.js)
+      // 2. Module initialization is synchronous (no top-level await in ./matrix/monitor/index.js)
       // 3. The lock only serializes the import phase, not the provider startup
       const previousLock = matrixStartupLock;
       let releaseLock: () => void = () => {};
@@ -445,9 +445,9 @@ export const matrixPlugin: ChannelPlugin<ResolvedMatrixAccount> = {
 
       // Lazy import: the monitor pulls the reply pipeline; avoid ESM init cycles.
       // Wrap in try/finally to ensure lock is released even if import fails.
-      let monitorMatrixProvider: typeof import("./matrix/index.js").monitorMatrixProvider;
+      let monitorMatrixProvider: typeof import("./matrix/monitor/index.js").monitorMatrixProvider;
       try {
-        const module = await import("./matrix/index.js");
+        const module = await import("./matrix/monitor/index.js");
         monitorMatrixProvider = module.monitorMatrixProvider;
       } finally {
         // Release lock after import completes or fails

extensions/matrix/src/matrix/monitor/handler.media-failure.test.ts

@@ -104,6 +104,7 @@ function createHandlerHarness() {
     directTracker: {
       isDirectMessage: vi.fn().mockResolvedValue(true),
     },
+    dropPreStartupMessages: true,
     getRoomInfo: vi.fn().mockResolvedValue({
       name: "Media Room",
       canonicalAlias: "#media:example.org",

extensions/matrix/src/matrix/monitor/handler.test.ts

@@ -594,6 +594,7 @@ describe("matrix monitor handler pairing account scope", () => {
       directTracker: {
         isDirectMessage: async () => false,
       },
+      dropPreStartupMessages: true,
       getRoomInfo: async () => ({ altAliases: [] }),
       getMemberDisplayName: async () => "sender",
       needsRoomAliasesForConfig: false,

extensions/matrix/src/matrix/monitor/handler.thread-root-media.test.ts

@@ -119,6 +119,7 @@ describe("createMatrixRoomMessageHandler thread root media", () => {
       directTracker: {
         isDirectMessage: vi.fn().mockResolvedValue(true),
       },
+      dropPreStartupMessages: true,
       getRoomInfo: vi.fn().mockResolvedValue({
         name: "Media Room",
         canonicalAlias: "#media:example.org",

test/helpers/extensions/plugin-routing.ts

@@ -0,0 +1,7 @@
+export {
+  __testing as sessionBindingTesting,
+  registerSessionBindingAdapter,
+} from "../../../src/infra/outbound/session-binding-service.js";
+export { setActivePluginRegistry } from "../../../src/plugins/runtime.js";
+export { resolveAgentRoute } from "../../../src/routing/resolve-route.js";
+export { createTestRegistry } from "../../../src/test-utils/channel-plugins.js";