Add native Windows compatibility for config, bootstrap, and CLI.

Support profile-based config resolution with auto-selection of a sole profile,
native IPA.exe -n bootstrap on Windows, platform-aware process cleanup, and
Windows-friendly userdata backup path inference.

Co-authored-by: Cursor <cursoragent@cursor.com>

plugin-helper.windows.toml.example

@@ -0,0 +1,5 @@
+[[profiles]]
+id = "windows"
+label = "Native Windows BSManager"
+instances_root = "~/BSManager/BSInstances"
+state_dir = ".state"