fix: ignore IME composition Enter in chat search (#26172) (#26238)

Pressing Enter to confirm an IME composition (e.g. Japanese, Chinese, or Korean)
in the chat search modal and the sidebar search input was treated as a normal
Enter and triggered a search action such as starting a new chat, instead of just
confirming the composed text.

Guard the search keydown handlers so a keydown fired while composing is ignored:
- SearchInput.svelte on:keydown
- SearchModal.svelte document-level onKeyDown
using e.isComposing (with a keyCode === 229 fallback), mirroring the IME guard
already used by MessageInput. A second Enter, after the composition is confirmed,
still triggers the action as before.

Fixes #26172

Co-authored-by: Yogi <251807336+ybnjm1234-source@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

src/lib/components/layout/SearchModal.svelte

@@ -176,6 +176,12 @@
 	}
 
 	const onKeyDown = (e) => {
+		// Ignore keydown fired while confirming an IME composition (e.g. Japanese/Chinese/Korean)
+		// so confirming the composition with Enter doesn't trigger search actions (#26172).
+		if (e.isComposing || e.keyCode === 229) {
+			return;
+		}
+
 		const searchOptions = document.getElementById('search-options-container');
 		if (searchOptions || !show) {
 			return;

src/lib/components/layout/Sidebar/SearchInput.svelte

@@ -229,6 +229,12 @@
 				}
 			}}
 			on:keydown={(e) => {
+				// Ignore keydown fired while confirming an IME composition (e.g. Japanese/Chinese/Korean)
+				// so confirming the composition with Enter doesn't trigger search actions (#26172).
+				if (e.isComposing || e.keyCode === 229) {
+					return;
+				}
+
 				if (e.key === 'Enter') {
 					if (filteredItems.length > 0) {
 						const itemElement = document.getElementById(`search-item-${selectedIdx}`);