fix(look-at): handle JSON parse errors from session.prompt gracefully (#1216)

When multimodal-looker agent returns empty/malformed response, the SDK
throws 'JSON Parse error: Unexpected EOF'. This commit adds try-catch
around session.prompt() to provide user-friendly error message with
troubleshooting guidance.

- Add error handling for JSON parse errors with detailed guidance
- Add error handling for generic prompt failures
- Add test cases for both error scenarios

src/tools/look-at/tools.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test"
-import { normalizeArgs, validateArgs } from "./tools"
+import { normalizeArgs, validateArgs, createLookAt } from "./tools"
 
 describe("look-at tool", () => {
   describe("normalizeArgs", () => {
@@ -70,4 +70,80 @@ describe("look-at tool", () => {
       expect(error).toContain("file_path")
     })
   })
+
+  describe("createLookAt error handling", () => {
+    // #given session.prompt에서 JSON parse 에러 발생
+    // #when LookAt 도구 실행
+    // #then 사용자 친화적 에러 메시지 반환
+    test("handles JSON parse error from session.prompt gracefully", async () => {
+      const mockClient = {
+        session: {
+          get: async () => ({ data: { directory: "/project" } }),
+          create: async () => ({ data: { id: "ses_test_json_error" } }),
+          prompt: async () => {
+            throw new Error("JSON Parse error: Unexpected EOF")
+          },
+          messages: async () => ({ data: [] }),
+        },
+      }
+
+      const tool = createLookAt({
+        client: mockClient,
+        directory: "/project",
+      } as any)
+
+      const toolContext = {
+        sessionID: "parent-session",
+        messageID: "parent-message",
+        agent: "sisyphus",
+        abort: new AbortController().signal,
+      }
+
+      const result = await tool.execute(
+        { file_path: "/test/file.png", goal: "analyze image" },
+        toolContext
+      )
+
+      expect(result).toContain("Error: Failed to analyze file")
+      expect(result).toContain("malformed response")
+      expect(result).toContain("multimodal-looker")
+      expect(result).toContain("image/png")
+    })
+
+    // #given session.prompt에서 일반 에러 발생
+    // #when LookAt 도구 실행
+    // #then 원본 에러 메시지 포함한 에러 반환
+    test("handles generic prompt error gracefully", async () => {
+      const mockClient = {
+        session: {
+          get: async () => ({ data: { directory: "/project" } }),
+          create: async () => ({ data: { id: "ses_test_generic_error" } }),
+          prompt: async () => {
+            throw new Error("Network connection failed")
+          },
+          messages: async () => ({ data: [] }),
+        },
+      }
+
+      const tool = createLookAt({
+        client: mockClient,
+        directory: "/project",
+      } as any)
+
+      const toolContext = {
+        sessionID: "parent-session",
+        messageID: "parent-message",
+        agent: "sisyphus",
+        abort: new AbortController().signal,
+      }
+
+      const result = await tool.execute(
+        { file_path: "/test/file.pdf", goal: "extract text" },
+        toolContext
+      )
+
+      expect(result).toContain("Error: Failed to send prompt")
+      expect(result).toContain("Network connection failed")
+    })
+  })
 })