test(server): expand workspace routing fixed-id coverage (#26458)

packages/opencode/test/fixture/flag.ts

@@ -0,0 +1,20 @@
+import type { WorkspaceID } from "@/control-plane/schema"
+import { Flag } from "@opencode-ai/core/flag/flag"
+import { Effect, Scope } from "effect"
+
+/**
+ * Scoped override for `Flag.OPENCODE_WORKSPACE_ID`. Saves the previous value
+ * on entry and restores it via finalizer when the surrounding scope closes —
+ * preserves the original try/finally semantics regardless of test outcome.
+ */
+export function withFixedWorkspaceID(id: WorkspaceID): Effect.Effect<void, never, Scope.Scope> {
+  return Effect.gen(function* () {
+    const previous = Flag.OPENCODE_WORKSPACE_ID
+    Flag.OPENCODE_WORKSPACE_ID = id
+    yield* Effect.addFinalizer(() =>
+      Effect.sync(() => {
+        Flag.OPENCODE_WORKSPACE_ID = previous
+      }),
+    )
+  })
+}