feat: wire Monaco editor to real file read/write

Co-Authored-By: Claude <noreply@anthropic.com>

web/src/lib/api/files.ts

@@ -1,4 +1,10 @@
-import { useQuery, type UseQueryResult } from "@tanstack/react-query";
+import {
+  useMutation,
+  useQuery,
+  useQueryClient,
+  type UseMutationResult,
+  type UseQueryResult,
+} from "@tanstack/react-query";
 
 import { apiClient } from "@/lib/api/client";
 
@@ -31,6 +37,11 @@ export function inferLanguage(name: string): string | undefined {
   return ext ? LANGUAGE_BY_EXTENSION[ext] : undefined;
 }
 
+export interface ReadFileResponse {
+  path: string;
+  content: string;
+}
+
 function fileListQueryKey(workspaceId: string, path: string) {
   return ["workspaces", workspaceId, "files", path || "."] as const;
 }
@@ -50,6 +61,35 @@ async function fetchFileList(
   return (await res.json()) as FileEntry[];
 }
 
+export function fileReadQueryKey(workspaceId: string, path: string) {
+  return ["workspaces", workspaceId, "files", "read", path] as const;
+}
+
+async function fetchFileRead(
+  workspaceId: string,
+  path: string,
+): Promise<ReadFileResponse> {
+  const url =
+    `/api/workspaces/${encodeURIComponent(workspaceId)}/files/read?` +
+    new URLSearchParams({ path }).toString();
+  const res = await apiClient(url);
+  if (!res.ok) {
+    throw new Error(`Failed to read file: ${res.status}`);
+  }
+  return (await res.json()) as ReadFileResponse;
+}
+
+export function useFileRead(
+  workspaceId: string | null,
+  path: string | null,
+): UseQueryResult<ReadFileResponse, Error> {
+  return useQuery({
+    queryKey: fileReadQueryKey(workspaceId ?? "", path ?? ""),
+    queryFn: () => fetchFileRead(workspaceId!, path!),
+    enabled: !!workspaceId && !!path,
+  });
+}
+
 export function useFileList(
   workspaceId: string | null,
   path: string,
@@ -62,3 +102,29 @@ export function useFileList(
     enabled: !!workspaceId && enabled,
   });
 }
+
+export function useFileWrite(): UseMutationResult<
+  void,
+  Error,
+  { path: string; content: string; workspaceId: string }
+> {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: async ({ workspaceId, path, content }) => {
+      const url = `/api/workspaces/${encodeURIComponent(workspaceId)}/files/write`;
+      const res = await apiClient(url, {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ path, content }),
+      });
+      if (!res.ok) {
+        throw new Error(`Failed to save file: ${res.status}`);
+      }
+    },
+    onSuccess: (_, variables) => {
+      queryClient.invalidateQueries({
+        queryKey: fileReadQueryKey(variables.workspaceId, variables.path),
+      });
+    },
+  });
+}