web(coder UI): ChatInput migration + Thinking render + DiffPanel route fix

Bundles in-progress working-tree UI work not authored this session (CoderPane ChatInput migration, AgentComposerBar/CoderMessageList/tab-bar/sidebar/pane refinements, provider icons) with this session's changes to the same files: MessageBubble renders a collapsible 'Thinking' block from reasoning_text/reasoning_parts (surfacing ACP agent_thought_chunk + native reasoning), and the DiffPanel approve/reject calls are repointed to the real /api/coder/pending/:id/apply and /reject routes (the old /sessions/:id/pending/:id/approve|reject paths did not exist).

apps/web/src/hooks/useSidebarDrawer.tsx

@@ -1,6 +1,7 @@
 import { createContext, useCallback, useContext, useEffect, useState } from 'react';
 import type { ReactNode } from 'react';
 import { useLocation } from 'react-router-dom';
+import { useViewport } from './useViewport';
 
 interface SidebarDrawerState {
   open: boolean;
@@ -13,13 +14,17 @@ const Ctx = createContext<SidebarDrawerState | null>(null);
 export function SidebarDrawerProvider({ children }: { children: ReactNode }) {
   const [open, setOpen] = useState(false);
   const location = useLocation();
+  const { isMobile } = useViewport();
 
-  // Auto-close on navigation. Effect fires once on mount too (open default
-  // is false, so no observable effect) and on every pathname change after.
   useEffect(() => {
     setOpen(false);
   }, [location.pathname]);
 
+  // Close drawer on orientation change (landscape→portrait transition).
+  useEffect(() => {
+    setOpen(false);
+  }, [isMobile]);
+
   const toggle = useCallback(() => setOpen((v) => !v), []);
 
   return <Ctx.Provider value={{ open, setOpen, toggle }}>{children}</Ctx.Provider>;