fix: add null guards for output.output in tool.execute.after hooks

Three hooks crashed with TypeError when MCP tools returned results where
output.output is undefined. Added type guards to all affected hooks:

- comment-checker/hook.ts: guard before toLowerCase()
- edit-error-recovery/hook.ts: guard before toLowerCase()
- task-resume-info/hook.ts: guard before startsWith()/includes()/trimEnd()
- Added test for undefined output.output in edit-error-recovery

Fixes #1746

src/hooks/edit-error-recovery/index.test.ts

@@ -21,6 +21,17 @@ describe("createEditErrorRecoveryHook", () => {
       metadata: {},
     })
 
+    describe("#given output.output is undefined", () => {
+      //#when tool.execute.after is called
+      //#then should return without throwing
+      it("#then should not throw", async () => {
+        const input = createInput("Edit")
+        const output = { title: "Edit", output: undefined as unknown as string, metadata: {} }
+
+        await expect(hook["tool.execute.after"](input, output)).resolves.toBeUndefined()
+      })
+    })
+
     describe("#given Edit tool with oldString/newString same error", () => {
       describe("#when the error message is detected", () => {
         it("#then should append the recovery reminder", async () => {