refactor: remove legacy workspace runtime branches

backend/test/workspace-runtime-handoff.test.ts

@@ -55,18 +55,6 @@ function evidenceWorkspace(source: string, policy = ""): string {
 ${source}${policy}`;
 }
 
-const migrationRequiredWorkspace = canonicalWorkspace
-  .replace("schema_version: 3", "schema_version: 2")
-  .replace(
-    "    engine: qdrant\n    collection: psd-clinical",
-    "    engine: pgvector\n    database: analytics\n    schema: vectors\n    collection: documents",
-  )
-  .replace("    dimensions: 1024", "    dimensions: 768")
-  .replace("    distance: cosine", "    distance: cosine\n    supported_transports: [rest_api]")
-  .replace("    provider: ollama_internal", "    provider: ollama_compatible")
-  .replace("    model: qwen3-embedding:0.6b", "    model: nomic-embed-text")
-  .replace("    dimensions: 1024", "    dimensions: 768");
-
 afterEach(() => {
   vi.unstubAllEnvs();
   roots.splice(0).forEach((root) => rmSync(root, { recursive: true, force: true }));
@@ -377,15 +365,6 @@ test("static S3 Evidence resolves only configured secret-root file paths", async
   }
 });
 
-test("ThtRunner refuses to render a migration-required registry snapshot", async () => {
-  const f = await fixture(migrationRequiredWorkspace);
-  const runner = runnerFor(f);
-
-  expect(() => runner.acquireWorkspaceRuntime(f.revision.snapshotPath)).toThrow(
-    "Workspace descriptor requires explicit migration to schema version 3",
-  );
-});
-
 test("local GET sessions mine uses the real canonical handoff and returns an empty inventory", async () => {
   const f = await fixture();
   const app = buildApp(loadConfig({