fix(studio): forbid ext:: remotes; type the per-dialect test table

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/feature-studio/src/server/git.ts

@@ -11,6 +11,7 @@ const BASE = [
   "-c", "merge.conflictstyle=merge",
   "-c", "pull.rebase=false",
   "-c", "init.defaultBranch=main",
+  "-c", "protocol.ext.allow=never", // author-supplied remote URLs must never run commands
 ];
 
 function env(who?: Identity): Record<string, string> {

packages/feature-studio/test/feature.test.ts

@@ -11,7 +11,7 @@ test("anonymous gets 401, learners 403", async () => {
   expect((await env.call("lea", "POST", "/api/studio/courses", { id: "x", title: "X" })).status).toBe(403);
 });
 
-const DBS = [["sqlite", "sqlite://:memory:"], ...(process.env.STC_TEST_PG_URL ? [["postgres", process.env.STC_TEST_PG_URL]] : [])] as const;
+const DBS: [string, string][] = [["sqlite", "sqlite://:memory:"], ...(process.env.STC_TEST_PG_URL ? [["postgres", process.env.STC_TEST_PG_URL] as [string, string]] : [])];
 
 test.each(DBS)("creating a course records the creator in course_authors; a per-course author without the role can edit it [%s]", async (_name, url) => {
   env = await setupApp([], url);

packages/feature-studio/test/publish.test.ts

@@ -144,3 +144,12 @@ describe("sync", () => {
     void bob;
   });
 });
+
+test("ext:: remotes cannot run commands", async () => {
+  const { store } = await courseWithEdit();
+  const marker = join(tempDir(), "pwned");
+  await store.setRemote("c1", `ext::touch%s${marker}`);
+  const r = await store.sync("c1", ada);
+  expect(r.ok).toBe(false);
+  expect(await Bun.file(marker).exists()).toBe(false);
+});