fix(app): terminal disconnect and resync (#14004)

packages/app/src/utils/terminal-writer.test.ts

@@ -6,7 +6,10 @@ describe("terminalWriter", () => {
     const calls: string[] = []
     const scheduled: VoidFunction[] = []
     const writer = terminalWriter(
-      (data) => calls.push(data),
+      (data, done) => {
+        calls.push(data)
+        done?.()
+      },
       (flush) => scheduled.push(flush),
     )
 
@@ -24,10 +27,38 @@ describe("terminalWriter", () => {
   test("flush is a no-op when empty", () => {
     const calls: string[] = []
     const writer = terminalWriter(
-      (data) => calls.push(data),
+      (data, done) => {
+        calls.push(data)
+        done?.()
+      },
       (flush) => flush(),
     )
     writer.flush()
     expect(calls).toEqual([])
   })
+
+  test("flush waits for pending write completion", () => {
+    const calls: string[] = []
+    let done: VoidFunction | undefined
+    const writer = terminalWriter(
+      (data, finish) => {
+        calls.push(data)
+        done = finish
+      },
+      (flush) => flush(),
+    )
+
+    writer.push("a")
+
+    let settled = false
+    writer.flush(() => {
+      settled = true
+    })
+
+    expect(calls).toEqual(["a"])
+    expect(settled).toBe(false)
+
+    done?.()
+    expect(settled).toBe(true)
+  })
 })