fix(install-windows): ask before downloading models instead of offering Ctrl+C

Ctrl+C in PS 5.1 kills the whole script, so the advertised way to skip the
download was also the way to abort the install before its final steps. Now a
'Download them now? [Y/n]' prompt, so declining continues to the end. The
default-model seed moves above the pull - it only writes a settings row and was
being lost along with the download. A test forbids offering Ctrl+C again.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_smoke.py

@@ -95,6 +95,12 @@ def test_ncp_is_registered_on_path_not_in_a_shell_profile():
     assert ps1.index("ollama pull") > ps1.index("Creating desktop shortcut"), \
         "model pull must come after the desktop shortcut"
 
+    # And it must not TELL anyone to press Ctrl+C: in PS 5.1 that kills the
+    # script, so the advertised way to skip the download was also the way to
+    # abort the install. Skipping is a prompt now. Comments stripped so the
+    # comment explaining this does not trip the check.
+    assert "Ctrl+C" not in code, "installer must not offer Ctrl+C as a skip"
+
 
 def test_no_ps1_shadows_the_ncp_path_shim():
     """PowerShell resolves ExternalScript (.ps1) ahead of Application (.cmd), so