perf(terminal): keep uncontended paste delivery synchronous

src/renderer/src/components/terminal-pane/terminal-paste-operation-order.test.ts

@@ -32,6 +32,16 @@ function chunkedWindowsPaste() {
 }
 
 describe('terminal paste operation ordering', () => {
+  it('starts an uncontended paste operation synchronously', async () => {
+    let started = false
+    const operation = runTerminalPtyInputTransaction('pty-1', async () => {
+      started = true
+    })
+
+    expect(started).toBe(true)
+    await operation
+  })
+
   it('keeps startup context outside an active chunked user paste frame', async () => {
     const writes: string[] = []
     let startupDraft: Promise<boolean> | null = null

src/renderer/src/components/terminal-pane/terminal-pty-input-transaction.ts

@@ -8,14 +8,16 @@ export async function runTerminalPtyInputTransaction<T>(
     return await operation()
   }
 
-  const previous = transactionTails.get(ptyId) ?? Promise.resolve()
+  const previous = transactionTails.get(ptyId)
   let release!: () => void
   const current = new Promise<void>((resolve) => {
     release = resolve
   })
   transactionTails.set(ptyId, current)
 
-  await previous
+  if (previous) {
+    await previous
+  }
   try {
     return await operation()
   } finally {