fix(native-chat): anchor marker stripping to a contiguous image-source run

Re-home the landed literal-text counts onto the draft reconciler after the
#14665 revert removed the module they lived in, and cover the anchoring
boundary: a marker the user typed must not absorb a later send's image.

mobile/src/session/mobile-native-chat-draft-reconcile.test.ts

@@ -5,6 +5,7 @@ import {
   findLandedImagePreviewEchoes,
   findLandedUnconfirmedSends,
   migrateImagePreviewMessageIds,
+  userTextOccurrenceCounts,
   type PendingImagePreviewEcho,
   type UnconfirmedSend
 } from './mobile-native-chat-draft-reconcile'
@@ -234,3 +235,22 @@ describe('mobile native chat image preview reconciliation', () => {
     ).toEqual({ [sessionKey]: { prompt: ['file:///a.jpg'] } })
   })
 })
+
+describe('userTextOccurrenceCounts', () => {
+  it('counts a literal marker turn under its verbatim text', () => {
+    expect(userTextOccurrenceCounts([userText('u1', 'keep [Image #1] literal')])).toEqual(
+      new Map([['keep [Image #1] literal', 1]])
+    )
+  })
+
+  // An attached-image turn must not retire a send that carried no images.
+  it('excludes a folded image turn from the literal landed counts', () => {
+    const counts = userTextOccurrenceCounts([
+      userText('s1', '[Image: source: /tmp/a.png]'),
+      userText('p1', '[Image #1] look')
+    ])
+
+    expect(counts.get('look')).toBeUndefined()
+    expect(counts.size).toBe(0)
+  })
+})

mobile/src/session/mobile-native-chat-draft-reconcile.ts

@@ -49,6 +49,24 @@ export function countUserTextOccurrences(
   return count
 }
 
+/** Landed literal-text turns counted under the same key a markerless send uses.
+ *  Image turns are excluded so they cannot retire a send that carried none. */
+export function userTextOccurrenceCounts(
+  messages: readonly NativeChatMessage[]
+): Map<string, number> {
+  const counts = new Map<string, number>()
+  for (const message of normalizeImageTranscriptMessages(messages)) {
+    if (message.blocks.some(isImageRefBlock)) {
+      continue
+    }
+    const text = nativeChatUserMessageMatchText(message)
+    if (text) {
+      counts.set(text, (counts.get(text) ?? 0) + 1)
+    }
+  }
+  return counts
+}
+
 /** Number of `[Image: source: …]` echo turns strictly after `tailId` (or the
  *  whole transcript when the tail was paginated out). An image-only send has no
  *  caption to match, so it reconciles by ordinal against this count — counting

src/shared/native-chat-image-transcript-markers.test.ts

@@ -217,6 +217,48 @@ describe('normalizeImageTranscriptMessages', () => {
     expect(out[2]).toBe(after)
   })
 
+  it('keeps a later literal marker when earlier turns separate it from a real image send', () => {
+    const out = normalizeImageTranscriptMessages([
+      userText('s1', '[Image: source: /tmp/a.jpg]'),
+      userText('p1', '[Image #1] what is this?'),
+      userText('u1', 'thanks'),
+      userText('u2', 'in my notes I wrote [Image #2] as plain text')
+    ])
+
+    expect(out.at(-1)?.blocks).toEqual([
+      { type: 'text', text: 'in my notes I wrote [Image #2] as plain text' }
+    ])
+  })
+
+  it('breaks the anchor when a non-image user turn separates the source run from the prompt', () => {
+    const out = normalizeImageTranscriptMessages([
+      userText('s1', '[Image: source: /tmp/a.jpg]'),
+      userText('u1', 'here is the picture'),
+      userText('u2', 'please preserve [Image #1] literally')
+    ])
+
+    expect(out.map((message) => message.blocks)).toEqual([
+      [{ type: 'image-ref', path: '/tmp/a.jpg' }],
+      [{ type: 'text', text: 'here is the picture' }],
+      [{ type: 'text', text: 'please preserve [Image #1] literally' }]
+    ])
+  })
+
+  // A marker the user typed must not absorb the image of the send that follows it.
+  it('does not let a literal marker turn claim a later send’s image source', () => {
+    const out = normalizeImageTranscriptMessages([
+      userText('u1', 'remember I typed [Image #1] by hand'),
+      userText('s1', '[Image: source: /tmp/a.jpg]'),
+      userText('p1', '[Image #1] what is this?')
+    ])
+
+    expect(out[0]?.blocks).toEqual([{ type: 'text', text: 'remember I typed [Image #1] by hand' }])
+    expect(out.at(-1)?.blocks).toEqual([
+      { type: 'image-ref', path: '/tmp/a.jpg' },
+      { type: 'text', text: 'what is this?' }
+    ])
+  })
+
   it('leaves assistant messages untouched', () => {
     const assistant: NativeChatMessage = {
       id: 'a',