fix(server): expand ~ in file-explorer scoped paths

Assistant markdown images with ~-prefixed paths hit ENOENT because
path.resolve doesn't expand ~, leaving paths like
workspaceRoot/~/rest-of-path that never resolve. Reuse the existing
resolvePathFromBase helper so tilde paths inside the workspace load
instead of getting stuck on the image spinner; the sandbox check still
rejects tilde paths that resolve outside the workspace.

packages/server/src/server/file-explorer/service.test.ts

@@ -4,6 +4,10 @@ import path from "node:path";
 import { describe, expect, it } from "vitest";
 import { listDirectoryEntries, readExplorerFile } from "./service.js";
 
+async function createHomeTempDir(prefix: string): Promise<string> {
+  return mkdtemp(path.join(os.homedir(), prefix));
+}
+
 async function createTempDir(prefix: string): Promise<string> {
   return mkdtemp(path.join(os.tmpdir(), prefix));
 }
@@ -97,6 +101,41 @@ describe("file explorer service", () => {
     }
   });
 
+  it("expands a ~ prefix in relative paths against the user home directory", async () => {
+    const root = await createHomeTempDir(".paseo-file-explorer-home-");
+
+    try {
+      const filePath = path.join(root, "sample.txt");
+      await writeFile(filePath, "hello from home\n", "utf-8");
+
+      const tildePath = `~/${path.relative(os.homedir(), filePath)}`;
+      const result = await readExplorerFile({
+        root,
+        relativePath: tildePath,
+      });
+
+      expect(result.kind).toBe("text");
+      expect(result.content).toBe("hello from home\n");
+    } finally {
+      await rm(root, { recursive: true, force: true });
+    }
+  });
+
+  it("rejects ~-prefixed paths that resolve outside the workspace", async () => {
+    const root = await mkdtemp(path.join(os.tmpdir(), "paseo-file-explorer-outside-home-"));
+
+    try {
+      await expect(
+        readExplorerFile({
+          root,
+          relativePath: "~/some/file.txt",
+        }),
+      ).rejects.toThrow("Access outside of workspace is not allowed");
+    } finally {
+      await rm(root, { recursive: true, force: true });
+    }
+  });
+
   it("rejects symlinked files that resolve outside the workspace", async () => {
     const root = await createTempDir("paseo-file-explorer-");
     const outsideRoot = await createTempDir("paseo-file-explorer-outside-");

packages/server/src/server/file-explorer/service.ts

@@ -1,5 +1,6 @@
 import { promises as fs } from "fs";
 import path from "path";
+import { resolvePathFromBase } from "../path-utils.js";
 
 export type ExplorerEntryKind = "file" | "directory";
 export type ExplorerFileKind = "text" | "image" | "binary";
@@ -207,7 +208,7 @@ export async function getDownloadableFileInfo({ root, relativePath }: ReadFilePa
 
 async function resolveScopedPath({ root, relativePath = "." }: ScopedPathParams): Promise<string> {
   const normalizedRoot = path.resolve(root);
-  const requestedPath = path.resolve(normalizedRoot, relativePath);
+  const requestedPath = resolvePathFromBase(normalizedRoot, relativePath);
   const relative = path.relative(normalizedRoot, requestedPath);
 
   if (relative !== "" && (relative.startsWith("..") || path.isAbsolute(relative))) {