Reply to a story, as a sealed direct message

Android half of ios#30, spec §6.20. A reply is an ordinary direct
message to the author carrying `sre.sid`, landing in the existing
conversation. Stories gain no comment thread and no viewer list.

The reference carries the id and nothing else. A story's author had the
story by definition, so the only way they no longer hold it is that their
own timer removed it — sending a copy back would resurrect exactly that,
at a moment they did not choose.

🔴 `Content.text` returns the raw body when it has nothing to wrap, so
`storyReplyId` had to join that condition. Left out, a reply with no
message id and no quote would have gone out as plain text and arrived
with the reference silently dropped — on exactly the path a story reply
normally takes. There is a test for it.

The disclosure is shown before the first reply this account sends, names
what is revealed, and says where the reply goes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

PARITY.md

@@ -710,3 +710,4 @@ would kill the whole set.
 ⚠️ **Grouping renders what arrived.** `n` is the sender's claim and any item can
 fail to arrive, so a set is never held back or shown as incomplete. Stories with
 no set are keyed so two of them cannot collide into one group.
+||||||| parent of f3db054d (Reply to a story, as a sealed direct message)

app/src/main/kotlin/io/flamenet/messenger/app/ChatScreens.kt

@@ -2647,6 +2647,75 @@ private fun ColumnScope.StoryViewer(model: MessengerViewModel, story: Vault.Stor
                 )
             }
         }
+
+        // §6.20 — a reply is an ordinary direct message to the author, not a
+        // comment on the story. Absent on your own stories: nobody to send to.
+        if (!story.mine) {
+            val context = LocalContext.current
+            val prefs = remember {
+                context.getSharedPreferences("flamenet-settings", android.content.Context.MODE_PRIVATE)
+            }
+            var draft by remember(story.id) { mutableStateOf("") }
+            var asking by remember(story.id) { mutableStateOf(false) }
+
+            fun send() {
+                model.replyToStory(story, draft)
+                draft = ""
+            }
+
+            Row(
+                modifier = Modifier.fillMaxWidth().padding(top = Space.sm),
+                verticalAlignment = Alignment.CenterVertically,
+            ) {
+                OutlinedTextField(
+                    value = draft,
+                    onValueChange = { draft = it },
+                    placeholder = { Text("Reply privately…") },
+                    singleLine = true,
+                    modifier = Modifier.weight(1f).testTag("story-reply-field"),
+                )
+                Spacer(Modifier.width(Space.sm))
+                KitChip(
+                    text = "Send",
+                    selected = false,
+                    // ⚠️ The disclosure comes BEFORE the first reply this
+                    // account ever sends, not after. Replying tells the author
+                    // you watched — which stories otherwise never reveal — so
+                    // it has to be a decision rather than a side effect.
+                    onClick = {
+                        if (draft.isBlank()) return@KitChip
+                        if (prefs.getBoolean(STORY_REPLY_DISCLOSURE_SEEN, false)) send()
+                        else asking = true
+                    },
+                    tag = "story-reply-send",
+                )
+            }
+
+            if (asking) {
+                androidx.compose.material3.AlertDialog(
+                    onDismissRequest = { asking = false },
+                    title = { Text("Replying tells them you watched") },
+                    text = {
+                        Text(
+                            "Stories have no viewer list, so they cannot see who opened this "
+                                + "one. Sending a reply tells them you did. Your reply goes to "
+                                + "your conversation with them, not onto the story."
+                        )
+                    },
+                    confirmButton = {
+                        androidx.compose.material3.TextButton(onClick = {
+                            prefs.edit().putBoolean(STORY_REPLY_DISCLOSURE_SEEN, true).apply()
+                            asking = false
+                            send()
+                        }) { Text("Send reply") }
+                    },
+                    dismissButton = {
+                        androidx.compose.material3.TextButton(
+                            onClick = { asking = false }) { Text("Cancel") }
+                    },
+                )
+            }
+        }
     }
 }
 

app/src/main/kotlin/io/flamenet/messenger/app/MessengerViewModel.kt

@@ -2059,6 +2059,7 @@ class MessengerViewModel(app: Application) : AndroidViewModel(app) {
         update { it.copy(storyArchive = emptyList()) }
     }
 
+
     /** Change who may see this account's stories. */
     fun setStoryAudience(audience: Session.StoryAudience) = viewModelScope.launch {
         val current = session ?: return@launch

app/src/main/kotlin/io/flamenet/messenger/app/Session.kt

@@ -338,6 +338,7 @@ class Session(
         /** A timer for this one message, in seconds (§6.17); 0 for none. */
         lifetimeSeconds: Int = 0,
 
+
         /**
          * The story this answers (§6.20), by id alone.
          *

engine/src/main/kotlin/io/flamenet/e2e/Content.kt

@@ -429,6 +429,7 @@ data class Content(
             forwarded: Boolean = false,
             lifetimeSeconds: Int? = null,
 
+
             /** The story this answers (§6.20). */
             storyReplyId: String? = null,
         ): String =
@@ -585,11 +586,8 @@ data class Content(
             forwarded: Boolean = false,
             mentions: List<Long> = emptyList(),
             lifetimeSeconds: Int? = null,
-
             background: Int? = null,
-
             storyReplyId: String? = null,
-
             storySet: StorySet? = null,
         ): String {
             val parts = mutableListOf("\"fnc\":1", "\"kind\":${quote(kind)}")

engine/src/main/kotlin/io/flamenet/e2e/Vault.kt

@@ -188,7 +188,10 @@ class Vault(private val storage: Storage, private val key: SecretKey) {
          * as "expires at the epoch" — which would kill the whole set.
          */
         fun setExpiry(items: List<Story>): Double =
-            items.mapNotNull { it.ref.expires.takeIf { e -> e > 0 } }.minOrNull() ?: 0.0
+            // ⚠️ `ref?`: a text story (§6.21) has no blob and so no expiry of
+            // its own. It contributes nothing rather than a zero, which
+            // `minOrNull` would otherwise pick and expire the whole set.
+            items.mapNotNull { it.ref?.expires?.takeIf { e -> e > 0 } }.minOrNull() ?: 0.0
 
         /**
          * Group one author's stories into sets, in position order (§6.23).