fix(downloads): drop /select on Windows — opens wrong folder

Reported: clicking "Open Downloads folder" was opening the Documents
folder instead of Downloads. Root cause is the classic Windows
gotcha: when the path contains a space (e.g.
``C:\Users\Michael Dombaugh\Downloads``), Python's
``subprocess.Popen`` packs the ``/select,...`` argument into a single
quoted token, and Explorer's ``/select`` argument parser does NOT
accept that form — it silently falls back to whatever the user's
default Explorer view is (typically Documents).

Resolution paths considered:

- ``shell=True`` with a hand-built command string — works but opens
  the door to shell-injection if a file_name ever contained a quote
  or special char.
- ``cmd /c start "" explorer /select,...`` — same parsing issue.
- ctypes ShellExecuteW — pulls in a Windows-only dependency.
- **Skip /select. Open the folder directly.** ✓

Going with the last. ``explorer <folder>`` reliably opens the folder
regardless of spaces in the path; the user finds the freshly-saved
file by its name. The previous "highlight the file" nicety wasn't
worth the path-parsing fragility — every user folder on Windows is
``C:\Users\<name>`` and every Windows username can contain a space.

macOS keeps the ``open -R <file>`` reveal-in-Finder path because
macOS argument parsing is sane and that's a strict UX win.

2220 tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/gui/components/_legacy.py

@@ -258,14 +258,18 @@ def _open_in_file_manager(folder: "Path", *, select: "Path | None" = None) -> bo
     """Open the OS file manager at *folder*, optionally highlighting *select*.
 
     Windows
-        ``explorer /select,<file>`` is preferred when *select* is given —
-        Explorer pops to the foreground with the freshly-saved file
-        already highlighted. Falls back to ``explorer <folder>``, then
-        ``os.startfile`` if both fail; ``os.startfile`` is known to
-        silently no-op or open behind the active window in some Windows
-        configurations, which is why we don't lead with it.
+        ``explorer <folder>`` only. We deliberately do NOT use
+        ``explorer /select,<file>``: when the path contains a space
+        (e.g. ``C:\\Users\\Michael Dombaugh\\Downloads``), Python's
+        ``subprocess.Popen`` quotes the ``/select,...`` argument as one
+        unit, and Explorer's ``/select`` parser does not handle that
+        form — it silently falls back to opening the user's default
+        view (typically Documents). Opening the bare folder works
+        reliably regardless of spaces. ``os.startfile`` is kept as a
+        last-resort fallback only.
     macOS
-        ``open -R <file>`` reveals the file in Finder.
+        ``open -R <file>`` reveals the file in Finder when ``select``
+        is given; otherwise just opens the folder.
     Linux / *BSD
         ``xdg-open`` on the folder. No reliable cross-distro way to
         highlight a specific file.
@@ -278,19 +282,11 @@ def _open_in_file_manager(folder: "Path", *, select: "Path | None" = None) -> bo
     import subprocess
 
     if sys.platform == "win32":
-        # explorer.exe with /select wants a literal "/select," followed
-        # by the path — no space between the comma and the filename, or
-        # Explorer misinterprets and opens "My Computer" instead.
-        attempts = []
-        if select is not None:
-            attempts.append(["explorer", f"/select,{select}"])
-        attempts.append(["explorer", str(folder)])
-        for cmd in attempts:
         try:
-                subprocess.Popen(cmd)
+            subprocess.Popen(["explorer", str(folder)])
             return True
         except Exception:
-                continue
+            pass
         try:
             os.startfile(str(folder))  # type: ignore[attr-defined]
             return True