fix(webapp): normalize taskKind in API + drop unsafe casts in playground action

ApiRunListPresenter was returning `run.taskKind` raw from ClickHouse
where the column defaults to `""` for pre-migration rows, while the
dashboard's NextRunListPresenter normalizes to `"STANDARD"`. API
consumers and the dashboard now agree.

Playground action's two `as unknown as AuthenticatedEnvironment`
casts were redundant — `findEnvironmentBySlug` already returns
`Promise<AuthenticatedEnvironment | null>`. Drop the casts (and the
now-unused import) so a future change to the function's return shape
actually surfaces as a type error instead of crashing at runtime.

Author: ericallam

apps/webapp/app/presenters/v3/ApiRunListPresenter.server.ts

@@ -304,7 +304,10 @@ export class ApiRunListPresenter extends BasePresenter {
             durationMs: run.usageDurationMs,
             depth: run.depth,
             metadata,
-            taskKind: run.taskKind,
+            // ClickHouse defaults `task_kind` to "" for pre-migration rows.
+            // Match `NextRunListPresenter`'s "STANDARD" fallback so API
+            // consumers and the dashboard see the same value.
+            taskKind: run.taskKind || "STANDARD",
             ...ApiRetrieveRunPresenter.apiBooleanHelpersFromRunStatus(
               ApiRetrieveRunPresenter.apiStatusFromRunStatus(run.status, apiVersion)
             ),

apps/webapp/app/routes/resources.orgs.$organizationSlug.projects.$projectParam.env.$envParam.playground.action.tsx

@@ -10,7 +10,6 @@ import { requireUserId } from "~/services/session.server";
 import { EnvironmentParamSchema } from "~/utils/pathBuilder";
 import { mintSessionToken } from "~/services/realtime/mintSessionToken.server";
 import { ensureRunForSession } from "~/services/realtime/sessionRunManager.server";
-import type { AuthenticatedEnvironment } from "~/services/apiAuth.server";
 
 const PlaygroundAction = z.object({
   intent: z.enum(["create", "start", "save", "delete"]),
@@ -180,7 +179,7 @@ export const action = async ({ request, params }: ActionFunctionArgs) => {
 
       const ensureResult = await ensureRunForSession({
         session,
-        environment: environment as unknown as AuthenticatedEnvironment,
+        environment,
         reason: "initial",
       });
 
@@ -225,10 +224,7 @@ export const action = async ({ request, params }: ActionFunctionArgs) => {
         },
       });
 
-      const publicAccessToken = await mintSessionToken(
-        environment as unknown as AuthenticatedEnvironment,
-        chatId
-      );
+      const publicAccessToken = await mintSessionToken(environment, chatId);
 
       return json({
         runId: run.friendlyId,