fix(webapp): gate the session run's version on the basin the run will carry

The run is created with the organization's basin, and run-scoped stream routes
resolve their basin from the run alone. The session's own basin never enters
that path, so gating the version on it can stamp a run v2 whose basin resolves
to nothing, and every stream operation on that run then throws for its whole
life.

Reverts to the organization basin, which is the value the run is actually
created with. Where an organization has been deprovisioned, its sessions keep
serving v2 channels from their pinned basin while newly triggered runs degrade
to v1, which still works, rather than failing outright.

Author: matt-aitken

apps/webapp/app/services/realtime/sessionRunManager.server.ts

@@ -52,13 +52,7 @@ type EnsureRunForSessionParams = {
    */
   session: Pick<
     Session,
-    | "id"
-    | "friendlyId"
-    | "taskIdentifier"
-    | "triggerConfig"
-    | "currentRunId"
-    | "currentRunVersion"
-    | "streamBasinName"
+    "id" | "friendlyId" | "taskIdentifier" | "triggerConfig" | "currentRunId" | "currentRunVersion"
   >;
   environment: AuthenticatedEnvironment;
   reason: EnsureRunReason;
@@ -241,7 +235,6 @@ export async function ensureRunForSession(
       triggerConfig: true,
       currentRunId: true,
       currentRunVersion: true,
-      streamBasinName: true,
     },
   });
 
@@ -291,7 +284,7 @@ export async function ensureRunForSession(
  * degrades to v1 where v2 streams are not configured.
  */
 async function triggerSessionRun(params: {
-  session: Pick<Session, "id" | "taskIdentifier" | "streamBasinName">;
+  session: Pick<Session, "id" | "taskIdentifier">;
   config: SessionTriggerConfig;
   environment: AuthenticatedEnvironment;
   payloadOverrides?: Record<string, unknown>;
@@ -326,7 +319,7 @@ async function triggerSessionRun(params: {
     triggerAction: "trigger",
     realtimeStreamsVersion: determineRealtimeStreamsVersion(
       "v2",
-      session.streamBasinName ?? environment.organization.streamBasinName
+      environment.organization.streamBasinName
     ),
   });
 
@@ -348,13 +341,7 @@ type SwapSessionRunParams = {
    */
   session: Pick<
     Session,
-    | "id"
-    | "friendlyId"
-    | "taskIdentifier"
-    | "triggerConfig"
-    | "currentRunId"
-    | "currentRunVersion"
-    | "streamBasinName"
+    "id" | "friendlyId" | "taskIdentifier" | "triggerConfig" | "currentRunId" | "currentRunVersion"
   >;
   /**
    * The run requesting the swap. Optimistic claim requires