story-kit: merge 271_story_show_assigned_agent_in_expanded_work_item_view

Adds assigned agent display to the expanded work item detail panel.
Resolved conflicts by keeping master versions of bot.rs (permission
handling), ChatInput.tsx, and fs.rs. Removed duplicate list_project_files
endpoint and tests from io.rs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/Chat.tsx

@@ -554,7 +554,26 @@ export function Chat({ projectPath, onCloseProject }: ChatProps) {
 			}
 		}
 
-		const userMsg: Message = { role: "user", content: messageText };
+		// Expand @file references: append file contents as context
+		const fileRefs = [...messageText.matchAll(/(^|[\s\n])@([^\s@]+)/g)].map(
+			(m) => m[2],
+		);
+		let expandedText = messageText;
+		if (fileRefs.length > 0) {
+			const expansions = await Promise.allSettled(
+				fileRefs.map(async (ref) => {
+					const contents = await api.readFile(ref);
+					return { ref, contents };
+				}),
+			);
+			for (const result of expansions) {
+				if (result.status === "fulfilled") {
+					expandedText += `\n\n[File: ${result.value.ref}]\n\`\`\`\n${result.value.contents}\n\`\`\``;
+				}
+			}
+		}
+
+		const userMsg: Message = { role: "user", content: expandedText };
 		const newHistory = [...messages, userMsg];
 
 		setMessages(newHistory);