Document Wubi Shift-commit behavior as a known issue

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

README.md

@@ -15,3 +15,25 @@ Post-install initialization scripts, one directory per operating system.
   security-sensitive settings without an explicit opt-in.
 - Add a new OS by creating `<os>/` with `<os><version>-init.sh` and adding a
   row to the table above.
+
+## Known Issues
+
+### macOS: Wubi commits the candidate when switching to English
+
+While composing with the built-in Wubi input method (`com.apple.inputmethod.SCIM.WBX`),
+for example typing `wq` with the candidate `你` showing, pressing Shift to
+switch to English commits `你` instead of the raw letters `wq`.
+
+- Status: open. There is no system setting for it, and the state lives in the
+  input method's sandbox container, so `macos-init.sh` cannot configure it.
+- Workarounds: press Esc to cancel the composition before switching; press
+  Return (not verified); or switch to the ABC keyboard (Caps Lock or
+  Ctrl+Space) before typing.
+- Possible fix: use Squirrel (Rime) with `ascii_composer/switch_key: Shift_L:
+  commit_code` in `default.custom.yaml`. It must be installed manually, as the
+  repository forbids `curl | sh`.
+- Expected behavior: Shift during composition should commit the raw letters
+  and then switch to English; only Space, a number key, or Return should
+  confirm a candidate.
+- Upstream: the input method is built into macOS and maintained by Apple. Report
+  it through Feedback Assistant (macOS > Input Methods).