fix(git): render newly staged submodule pointer as new → <sha>

A staged submodule add records an all-zero head OID, which rendered as
0000000 → <sha>. Display the zero OID as "new" instead; the client
pointer label needs no change (N4).

src/server/git/gitService.test.ts

@@ -151,6 +151,18 @@ describe("gitStatus with submodules", () => {
     expect(status.submodules).not.toContain("HARL");
   });
 
+  it("renders a newly staged submodule pointer as new → <sha> (zero head OID)", async () => {
+    const { dir, c2 } = createFixture();
+    git(dir, ["submodule", "add", join(dir, "..", "origin"), "NEWSUB"]); // staged add: `1 A. S...` with a zero head OID
+
+    const status = await gitStatus(dir);
+    const pointer = status.files.find((file) => file.path === "NEWSUB");
+    expect(pointer?.index).toBe("added");
+    expect(pointer?.submoduleFromCommit).toBe("new");
+    expect(pointer?.submoduleToCommit).toBe(c2.slice(0, 7));
+    expect(status.submodules).toContain("NEWSUB");
+  });
+
   it("prefixes oldPath with the submodule path for renames inside a submodule", async () => {
     const { dir } = createFixture();
     git(join(dir, "HARL"), ["mv", "a.txt", "renamed.txt"]);

src/server/git/gitService.ts

@@ -85,7 +85,7 @@ async function expandSubmodule(cwd: string, sub: SubmoduleRecord): Promise<{ fil
       path: sub.path,
       index: sub.index,
       workingTree: sub.workingTree,
-      submoduleFromCommit: short(sub.headOid),
+      submoduleFromCommit: displayFromCommit(sub.headOid),
       submoduleToCommit: short(await resolveSubmoduleToCommit(cwd, sub)),
     });
   }
@@ -284,6 +284,11 @@ function short(oid: string): string {
   return oid.slice(0, 7);
 }
 
+/** A newly staged submodule records an all-zero head OID; display the pointer as `new → <sha>`. */
+function displayFromCommit(headOid: string): string {
+  return /^0+$/.test(headOid) ? "new" : short(headOid);
+}
+
 function hash(value: string): string {
   return createHash("sha1").update(value).digest("hex");
 }