fix(native-chat): a cancelled launch's unsent messages give their notes back

Closing a launch that never published handed its other unsent messages to a draft no chat shows,
and ended them as "returned", which cleared the notes they carried. They now end as discarded, so
their notes go back on the shelf as before; the text is still kept in that draft.

src/renderer/src/components/native-chat/structured-agent-session-outbox-chat-close.ts

@@ -1,8 +1,8 @@
 // What closing a chat does to its outbox: it never throws away a message the person sent. A
-// cancelled launch's own prompt, never sent, goes with the launch (its notes back on the shelf).
-// Any other message that never went out comes back to the conversation's draft, with its notes
-// following the text. One that went out may be the host's, so it stays and settles when the chat
-// is reopened.
+// cancelled launch's own prompt, never sent, goes with the launch. Any other message that never
+// went out comes back to the conversation's draft; its notes follow the text, except for a
+// cancelled launch, whose draft no chat shows, so they go back on the shelf. One that went out may
+// be the host's, so it stays and settles when the chat is reopened.
 
 import type { StructuredAgentSessionOutboxEntry } from '../../../../shared/structured-agent-session-outbox'
 import { structuredAgentSessionEntryAwaitsSettlement } from '../../../../shared/structured-agent-session-outbox-admission'
@@ -31,7 +31,7 @@ export function settleStructuredAgentSessionOutboxForClosedChat(
     } else if (!(options.cancelledLaunch && entry.source === 'launch')) {
       // The draft holds the text before the notes it carried are cleared.
       returnStructuredAgentSessionMessage(entry)
-      endStructuredAgentSessionEntry(entry, 'returned')
+      endStructuredAgentSessionEntry(entry, options.cancelledLaunch ? 'discarded' : 'returned')
     }
   }
   if (kept.length !== current.length) {

src/renderer/src/store/slices/tabs/structured-chat-close-keeps-outbox.test.tsx

@@ -55,6 +55,7 @@ import { resetStructuredAgentSessionCarriedNotesForTests } from '@/components/na
 import { useStructuredAgentSessionOutbox } from '@/components/native-chat/use-structured-agent-session-outbox'
 import { markStructuredAgentSessionLaunchCancelled } from '@/lib/structured-agent-session-launch-registry'
 import { isNoteInFlight } from '@/lib/notes-send-in-flight'
+import { subscribeToStructuredAgentSessionEntryEndings } from '@/components/native-chat/structured-agent-session-entry-endings'
 
 const WT = 'repo1::/path/wt1'
 const SID = 'session-close-1'
@@ -193,4 +194,24 @@ describe('closing a chat tab while the host is out of reach', () => {
     expect(draft()).toBe('')
     expect(isNoteInFlight('note-a')).toBe(false)
   })
+
+  // No chat shows a cancelled launch's draft, so a message typed into it gives its notes back.
+  it("ends a cancelled launch's other unsent messages as discarded, so their notes come back", () => {
+    const { store, chat } = seed()
+    markStructuredAgentSessionLaunchCancelled(WT, SID, 'local')
+    const typed = entry('TYPED-TEXT', { carriedNoteKeys: ['note-b'] })
+    writeOutbox(SID, [typed])
+    const endings: string[] = []
+    const unsubscribe = subscribeToStructuredAgentSessionEntryEndings((ended, ending) => {
+      if (ended.clientMessageId === typed.clientMessageId) {
+        endings.push(ending)
+      }
+    })
+
+    store.getState().closeUnifiedTab(chat.id)
+    unsubscribe()
+    expect(endings).toEqual(['discarded'])
+    expect(readOutbox(SID)).toEqual([])
+    expect(isNoteInFlight('note-b')).toBe(false)
+  })
 })