fix(web): don't enlarge on the Enter that commits an IME composition

Enter is also how a Japanese, Chinese or Korean input method commits the
candidate being composed. That keystroke means "accept this word", not
"new line", so the shortcut fired on every word such a user finished —
enlarging the field and inserting a stray newline each time.

Guard on event.nativeEvent.isComposing. The test pairs the composing case
with a negative control dispatching the same event with the flag off, so
a test that stopped reaching the handler cannot pass for the wrong reason.

Signed-off-by: cliffhall <cliff@futurescale.com>

clients/web/src/components/groups/SchemaForm/SchemaForm.test.tsx

@@ -2078,6 +2078,29 @@ describe("SchemaForm enlarge keyboard access (#2138)", () => {
     expect(noteField().tagName).toBe("INPUT");
   });
 
+  // Enter is also how an IME commits the candidate being composed, so acting on
+  // it there would enlarge the field and insert a newline every time a
+  // Japanese/Chinese/Korean user finished a word. userEvent has no composition
+  // mode, so the event is dispatched directly with the flag React reads.
+  it("ignores the Enter that commits an IME composition", () => {
+    renderWithMantine(<TwoStringHarness />);
+
+    fireEvent.keyDown(noteField(), { key: "Enter", isComposing: true });
+
+    expect(noteField().tagName).toBe("INPUT");
+    expect(noteField().value).toBe("");
+  });
+
+  // Same event without the flag, to prove the guard above is what turned it
+  // away rather than fireEvent simply not reaching the handler.
+  it("still enlarges on an Enter that is not composing", () => {
+    renderWithMantine(<TwoStringHarness />);
+
+    fireEvent.keyDown(noteField(), { key: "Enter", isComposing: false });
+
+    expect(noteField().tagName).toBe("TEXTAREA");
+  });
+
   it("leaves the field alone for any other key", async () => {
     const user = userEvent.setup();
     renderWithMantine(<TwoStringHarness />);

clients/web/src/components/groups/SchemaForm/SchemaForm.tsx

@@ -758,8 +758,16 @@ export function SchemaForm({
             // Ctrl/Cmd/Alt chords are deliberately left alone: those read as
             // "submit" in a form, and a consumer binding one (run the tool)
             // must not be overridden into enlarging a field instead.
+            //
+            // `isComposing` guards the IME case: Enter is also how a Japanese,
+            // Chinese or Korean input method commits the candidate being
+            // composed. That keystroke means "accept this word", not "new
+            // line", so acting on it would enlarge the field and insert a
+            // newline every time such a user finished a word — the shortcut
+            // would make the field unusable for them.
             if (
               event.key !== "Enter" ||
+              event.nativeEvent.isComposing ||
               event.ctrlKey ||
               event.metaKey ||
               event.altKey