refactor: modularize thread.tsx into focused component modules

- Split 1,089-line thread.tsx into 10 smaller, focused modules
- Created dedicated files for thinking-steps, welcome, composer, messages, etc.
- No breaking changes - all logic preserved exactly as before
- Improved code organization and maintainability

surfsense_web/components/assistant-ui/edit-composer.tsx

@@ -0,0 +1,27 @@
+import { ComposerPrimitive, MessagePrimitive } from "@assistant-ui/react";
+import type { FC } from "react";
+import { Button } from "@/components/ui/button";
+
+export const EditComposer: FC = () => {
+	return (
+		<MessagePrimitive.Root className="aui-edit-composer-wrapper mx-auto flex w-full max-w-(--thread-max-width) flex-col px-2 py-3">
+			<ComposerPrimitive.Root className="aui-edit-composer-root ml-auto flex w-full max-w-[85%] flex-col rounded-2xl bg-muted">
+				<ComposerPrimitive.Input
+					className="aui-edit-composer-input min-h-14 w-full resize-none bg-transparent p-4 text-foreground text-sm outline-none"
+					autoFocus
+				/>
+				<div className="aui-edit-composer-footer mx-3 mb-3 flex items-center gap-2 self-end">
+					<ComposerPrimitive.Cancel asChild>
+						<Button variant="ghost" size="sm">
+							Cancel
+						</Button>
+					</ComposerPrimitive.Cancel>
+					<ComposerPrimitive.Send asChild>
+						<Button size="sm">Update</Button>
+					</ComposerPrimitive.Send>
+				</div>
+			</ComposerPrimitive.Root>
+		</MessagePrimitive.Root>
+	);
+};
+