Chore: Add changeset for file operation error handling fix

Author: FL4TLiN3

.changeset/fix-file-operation-error-handling.md

@@ -0,0 +1,5 @@
+---
+"@perstack/runtime": patch
+---
+
+Handle file read errors gracefully in resolving PDF and image file states

packages/runtime/src/states/resolving-image-file.test.ts

@@ -121,7 +121,10 @@ describe("@perstack/runtime: StateMachineLogic['ResolvingImageFile']", () => {
       skillManagers: {},
     })
     expect(result.type).toBe("finishToolCall")
-    expect(result.newMessages[0].contents[0].contents[0]).toMatchObject({
+    if (result.type !== "finishToolCall") throw new Error("Unexpected event type")
+    const toolResultPart = result.newMessages[0].contents[0]
+    if (toolResultPart.type !== "toolResultPart") throw new Error("Unexpected part type")
+    expect(toolResultPart.contents[0]).toMatchObject({
       type: "textPart",
       text: expect.stringContaining('Failed to read image file "/nonexistent.png"'),
     })

packages/runtime/src/states/resolving-pdf-file.test.ts

@@ -132,6 +132,7 @@ describe("@perstack/runtime: StateMachineLogic['ResolvingPdfFile']", () => {
       skillManagers: {},
     })
     expect(result.type).toBe("finishToolCall")
+    if (result.type !== "finishToolCall") throw new Error("Unexpected event type")
     const userMessage = result.newMessages[1]
     expect(userMessage.contents[0]).toMatchObject({
       type: "textPart",