Address review feedback: dead code, comments, tracker field docs

#2: Remove empty if-block for is_existing_child_placeholder in controller.rs
#3: Remove dead selected_conversation_id/root_identity bindings in shared_session.rs
#4: Simplify ensure_remote_child_conversation comment to focus on idempotence
#10/#11: Update tracker field comments to use Primary/Observer terminology
    and explain when None

Co-Authored-By: Oz <oz-agent@warp.dev>

Author: cephalonaut

app/src/ai/blocklist/agent_view/controller.rs

@@ -857,8 +857,6 @@ impl AgentViewController {
         let is_new = exchange_count == 0
             && !(FeatureFlag::OrchestrationUnifiedStack.is_enabled()
                 && is_existing_child_placeholder);
-        if is_existing_child_placeholder {
-        }
         ctx.emit(AgentViewControllerEvent::EnteredAgentView {
             conversation_id,
             is_new,

app/src/ai/blocklist/controller/shared_session.rs

@@ -165,19 +165,6 @@ impl BlocklistAIController {
                     h.start_new_conversation(terminal_surface_id, false, true, false, ctx)
                 })
             });
-        let selected_conversation_id = self.context_model.as_ref(ctx).selected_conversation_id(ctx);
-        let root_identity =
-            history
-                .as_ref(ctx)
-                .conversation(&conversation_id)
-                .map(|conversation| {
-                    (
-                        conversation.get_root_task_id().clone(),
-                        conversation
-                            .get_root_task()
-                            .is_some_and(|task| task.source().is_some()),
-                    )
-                });
         if self.should_skip_replayed_response_for_existing_conversation(
             existing_conversation_id,
             &init_event.request_id,

app/src/ai/blocklist/history_model.rs

@@ -568,12 +568,10 @@ impl BlocklistAIHistoryModel {
         conversation_id
     }
 
-    /// Returns the single durable conversation mapping for a remotely hosted
-    /// child, creating it from fetched task metadata when necessary.
-    ///
-    /// Both Primary and Observer discovery call this method, so racing
-    /// `ChildStarted`, lifecycle, and viewer metadata callbacks converge on
-    /// the same run-id index entry.
+    /// Returns the existing run-id mapping for a remote child, creating one
+    /// from the supplied task metadata if none exists yet. Idempotent: racing
+    /// `ChildStarted`, lifecycle, and viewer metadata callbacks all converge
+    /// on the same entry.
     #[allow(clippy::too_many_arguments)]
     pub fn ensure_remote_child_conversation(
         &mut self,

app/src/ai/blocklist/orchestration_event_streamer.rs

@@ -222,9 +222,10 @@ struct ConversationStreamState {
     /// Consecutive `get_ambient_agent_task` failure count for the
     /// post-restore retry loop; resets on success.
     restore_fetch_failures: usize,
-    /// Owner-mode child tracker for this orchestrator family. Created lazily
-    /// by the flag-on family drain (`OrchestrationUnifiedStack`); `None` on
-    /// the flag-off baseline, where the legacy `drain_sse_events` path runs.
+    /// Primary-mode child tracker for this orchestrator family. `None` until
+    /// the first flag-on family drain fires and the tracker is constructed;
+    /// on the flag-off baseline the legacy `drain_sse_events` path runs
+    /// without a tracker.
     tracker: Option<OrchestrationChildTracker>,
 }
 
@@ -265,10 +266,9 @@ struct OrchestratorStreamState {
     /// cursor, so a replay does not generate spurious `ChildSpawned` events
     /// for already-known children.
     seeded: bool,
-    /// Viewer-mode child tracker for this orchestrator family. Created lazily
-    /// by the flag-on family drain (`OrchestrationUnifiedStack`); `None` on
-    /// the flag-off baseline, where the legacy `drain_ancestor_events` path
-    /// runs.
+    /// Observer-mode child tracker for this orchestrator family. `None` until
+    /// the first flag-on viewer drain fires; on the flag-off baseline the
+    /// legacy `drain_ancestor_events` path runs without a tracker.
     tracker: Option<OrchestrationChildTracker>,
 }