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).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/components/ChatInput.tsx

@@ -22,6 +22,7 @@ import { AttachmentPreviewModal } from '@/components/AttachmentPreviewModal';
 import { FileMentionPopover } from '@/components/FileMentionPopover';
 import { DropOverlay } from '@/components/DropOverlay';
 import { AgentPicker } from '@/components/AgentPicker';
+import { AgentCommandsHint } from '@/components/AgentCommandsHint';
 import { ContextBar } from '@/components/ContextBar';
 import { SlashCommandPicker } from '@/components/SlashCommandPicker';
 import { isSlashCommandToken, parseSlashInput, slashQuery } from '@/lib/slash-command';
@@ -560,6 +561,9 @@ export function ChatInput({ disabled, projectId, agentId, onAgentChange, session
           ))}
         </div>
       )}
+      {skills.length > 0 && (
+        <AgentCommandsHint commands={skills.map((s) => ({ name: s.name, description: s.description }))} />
+      )}
       {/* Batch 9 toolbar — agent picker + quick-toggle menu. v1.11.5.1
           inlines ContextBar in the same row so the bar lives next to the
           picker rather than as a separate header above it. The row renders