fix(disk-space): promote rounded GiB boundary

Round MiB before selecting the display unit so low-disk warnings do not render boundary values as 1024 MiB. Adds regression coverage for the GiB boundary. Fixes #90245.

src/infra/disk-space.test.ts

@@ -77,4 +77,13 @@ describe("disk-space helpers", () => {
     expect(formatDiskSpaceBytes(420 * 1024 * 1024)).toBe("420 MiB");
     expect(formatDiskSpaceBytes(1536 * 1024 * 1024)).toBe("1.5 GiB");
   });
+
+  it("promotes MiB values that round up to 1024 into GiB", () => {
+    // mib in [1023.5, 1024) rounds to 1024; must render as GiB, not "1024 MiB".
+    expect(formatDiskSpaceBytes(Math.round(1023.6 * 1024 * 1024))).toBe("1.0 GiB");
+    expect(formatDiskSpaceBytes(Math.round(1023.9 * 1024 * 1024))).toBe("1.0 GiB");
+    expect(formatDiskSpaceBytes(1024 * 1024 * 1024)).toBe("1.0 GiB");
+    // Just below the rounding boundary still reads as MiB.
+    expect(formatDiskSpaceBytes(Math.round(1023.4 * 1024 * 1024))).toBe("1023 MiB");
+  });
 });

src/infra/disk-space.ts

@@ -65,8 +65,11 @@ export function tryReadDiskSpace(targetPath: string): DiskSpaceSnapshot | null {
 /** Formats byte counts for compact operator-facing disk-space warnings. */
 export function formatDiskSpaceBytes(bytes: number): string {
   const mib = bytes / (1024 * 1024);
-  if (mib < 1024) {
-    return `${Math.max(0, Math.round(mib))} MiB`;
+  // Round before choosing the unit so a value that rounds up to 1024 MiB is
+  // promoted to "1.0 GiB" instead of printing the impossible "1024 MiB".
+  const roundedMib = Math.max(0, Math.round(mib));
+  if (roundedMib < 1024) {
+    return `${roundedMib} MiB`;
   }
   const gib = mib / 1024;
   return `${gib.toFixed(gib < 10 ? 1 : 0)} GiB`;