fix: the download bar fits the terminal

A 2 GB part drew a 98-column line, and on an 80-column console every redraw wrapped and left a copy behind. The bar now shrinks to the width and goes below ten columns of room.

scripts/download.py

@@ -214,12 +214,9 @@ def download_file(
                     pct = downloaded * 100 // total
                     if pct != shown:
                         shown = pct
-                        bar = "=" * (pct // 2) + " " * (50 - pct // 2)
-                        print(
-                            f"\r  {label}[{bar}] {pct}% ({downloaded:,}/{total:,})",
-                            end="",
-                            flush=True,
-                        )
+                        columns = shutil.get_terminal_size((80, 24)).columns
+                        line = _progress_line(label, downloaded, total, columns)
+                        print(f"\r\033[K{line}", end="", flush=True)
 
     if live:
         print()
@@ -229,6 +226,19 @@ def download_file(
         raise ValueError(f"downloaded {downloaded} bytes, expected {expected_size}")
 
 
+def _progress_line(label: str, done: int, total: int, columns: int) -> str:
+    """One physical line shorter than the terminal: a wrapped line leaves a
+    copy of itself on every redraw, since \\r goes back one row only. The
+    bar shrinks first, then goes."""
+    pct = done * 100 // total
+    figures = f" {pct}% ({done / 1e6:,.0f}/{total / 1e6:,.0f} MB)"
+    room = min(50, columns - 1 - len(f"  {label}[]") - len(figures))
+    if room < 10:
+        return f"  {label}{figures.strip()}"[: columns - 1]
+    filled = room * pct // 100
+    return f"  {label}[{'=' * filled}{' ' * (room - filled)}]{figures}"
+
+
 def join_volumes(parts: list[Path], dest: Path) -> None:
     """Concatenate split volumes into one archive, streaming."""
     with open(dest, "wb") as out:

tests/test_download.py

@@ -252,6 +252,21 @@ class TestJoinVolumes(unittest.TestCase):
             self.assertEqual(zf.testzip(), None)
 
 
+class TestProgressLineWidth(unittest.TestCase):
+    """The bar was 98 columns for a 2 GB part: on an 80-column console each
+    redraw wrapped and left a line behind."""
+
+    def test_the_line_fits_every_width(self):
+        from download import _progress_line
+
+        for columns in (20, 40, 80, 120, 200):
+            for done in (0, 1_000_000_000, 2_000_000_000):
+                with self.subTest(columns=columns, done=done):
+                    line = _progress_line("part 1/2 ", done, 2_000_000_000, columns)
+                    self.assertLess(len(line), columns)
+                    self.assertIn("%", line)
+
+
 class TestStagingIsolation(unittest.TestCase):
     """Two downloads into one BIOS folder must not share a staging directory."""