fix(mobile): stop the chat pre-clear from wiping a just-pasted image

The text write set clearInputFirst unconditionally. On the image path that
Ctrl+U lands AFTER pasteMobileNativeChatImagePaths already pasted the image,
so the agent receives the text alone while acceptSend still renders the
thumbnail on the sent bubble — silent image loss.

Desktop's image path clears exactly once, before the paste, and never again;
mobile now matches: pre-clear only when nothing was deliberately pasted first.
The image paste already leads with its own Ctrl+U, so a launch-draft prefill
parked on the input line still cannot glue onto the message.

Pinned at both levels: the controller test drives the real send hook and
asserts clearInputFirst per branch, and the send module asserts the wire text
carries no leading \x15. The image-attachments test injects its own baseSend,
so it structurally could not observe this.

mobile/src/session/mobile-native-chat-send.test.ts

@@ -194,6 +194,27 @@ describe('sendMobileNativeChatMessage', () => {
     )
   })
 
+  it('sends the text verbatim when clearInputFirst is not set', async () => {
+    // An image send pastes the image (behind its own leading Ctrl+U) before this
+    // text write; a clear byte here would kill the pasted image off the input line.
+    const client = clientWithResponse({
+      id: 'request',
+      ok: true,
+      result: { send: { accepted: true } },
+      _meta: { runtimeId: 'runtime' }
+    })
+
+    await sendMobileNativeChatMessage({
+      client,
+      terminal: 'term',
+      text: 'what is this',
+      clearInputFirst: false
+    })
+    const sent = vi.mocked(client.sendRequest).mock.calls[0]?.[1] as { text: string }
+    expect(sent.text).toBe('what is this')
+    expect(sent.text.startsWith('\x15')).toBe(false)
+  })
+
   it('sends a single non-submitting Escape for prompt cancellation', async () => {
     const client = clientWithResponse({
       id: 'request',

mobile/src/session/use-mobile-native-chat-controller.test.ts

@@ -213,6 +213,27 @@ describe('useMobileNativeChatController handleNativeChatSend', () => {
     expect(restoreRejectedDraft).not.toHaveBeenCalled()
   })
 
+  it('pre-clears the input line for a text-only send but never for an image send', async () => {
+    // The image path pastes the image behind its OWN leading Ctrl+U and then calls
+    // this send; a second clear here wipes the image off the input line and the
+    // agent receives text alone while the echo bubble still shows the thumbnail.
+    sendWithOutcome.mockResolvedValue('accepted')
+
+    await act(async () => {
+      await controller!.handleNativeChatSend('answer')
+    })
+    expect(sendWithOutcome).toHaveBeenLastCalledWith(
+      expect.objectContaining({ text: 'answer', clearInputFirst: true })
+    )
+
+    await act(async () => {
+      await controller!.handleNativeChatSend('look', ['file:///a.jpg'])
+    })
+    expect(sendWithOutcome).toHaveBeenLastCalledWith(
+      expect.objectContaining({ text: 'look', clearInputFirst: false })
+    )
+  })
+
   it('holds an unknown-outcome send without posting the optimistic echo', async () => {
     sendWithOutcome.mockResolvedValue('unknown')
     let accepted = false

mobile/src/session/use-mobile-native-chat-message-send.ts

@@ -99,10 +99,13 @@ export function useMobileNativeChatMessageSend(args: {
         client,
         terminal: handle,
         text,
-        // Why: desktop-parity pre-clear. The stale-input heal above only fires for
-        // terminals a mobile image paste marked, so a desktop launch-draft prefill
-        // sitting on the input line would otherwise glue onto this message.
-        clearInputFirst: true,
+        // Why: pre-clear only when nothing was deliberately pasted first. The heal
+        // above fires only for terminals a mobile image paste marked, so a desktop
+        // launch-draft prefill parked on the input line would otherwise glue onto
+        // this message. An image send already led its own paste with Ctrl+U, and a
+        // second one here would wipe the image it just pasted (desktop's image path
+        // likewise clears once, before the paste, and never again).
+        clearInputFirst: !images?.length,
         deadline,
         ...(deviceTokenRef.current
           ? { mobileClient: { id: deviceTokenRef.current, type: 'mobile' } }