chore(tui): tighten todo-fix comments, drop dead archive call

- gateway handler: turnController always archives in recordMessageComplete,
  so the post-complete archiveTodosAtTurnEnd().forEach is dead code. Drop
  it and the now-unused import.
- turnController: collapse archive prepend into a single spread expression.
- gateway server: one-line comment for the tool.start todo skip.

tui_gateway/server.py

@@ -1040,15 +1040,9 @@ def _on_tool_start(sid: str, tool_call_id: str, name: str, args: dict):
             pass
         session.setdefault("tool_started_at", {})[tool_call_id] = time.time()
     if _tool_progress_enabled(sid):
-        # Don't echo args.todos on tool.start — for merge=true (or partial
-        # replacement) it's only the items being updated, not the full list,
-        # and would flicker the live count. tool.complete is the source of
-        # truth (always returns the full list from the tool result).
-        _emit(
-            "tool.start",
-            sid,
-            {"tool_id": tool_call_id, "name": name, "context": _tool_ctx(name, args)},
-        )
+        # tool.complete is the source of truth for todos (full list from the
+        # tool result). args.todos here may be a partial merge update.
+        _emit("tool.start", sid, {"tool_id": tool_call_id, "name": name, "context": _tool_ctx(name, args)})
 
 
 def _on_tool_complete(sid: str, tool_call_id: str, name: str, args: dict, result: str):

ui-tui/src/app/createGatewayEventHandler.ts

@@ -11,7 +11,6 @@ import { applyDelegationStatus, getDelegationState } from './delegationStore.js'
 import type { GatewayEventHandlerContext } from './interfaces.js'
 import { patchOverlayState } from './overlayStore.js'
 import { turnController } from './turnController.js'
-import { archiveTodosAtTurnEnd } from './turnStore.js'
 import { getUiState, patchUiState } from './uiStore.js'
 
 const NO_PROVIDER_RE = /\bNo (?:LLM|inference) provider configured\b/i
@@ -537,12 +536,6 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
         const { finalMessages, finalText, wasInterrupted } = turnController.recordMessageComplete(ev.payload ?? {})
 
         if (!wasInterrupted) {
-          // Defensive: turnController.recordMessageComplete already prepends
-          // the archive at the head of finalMessages. This is a no-op in the
-          // normal path (state.todos is empty) but covers any edge where
-          // todos linger past the controller archive.
-          archiveTodosAtTurnEnd().forEach(appendMessage)
-
           const msgs: Msg[] = finalMessages.length ? finalMessages : [{ role: 'assistant', text: finalText }]
           msgs.forEach(appendMessage)
 

ui-tui/src/app/turnController.ts

@@ -469,12 +469,13 @@ class TurnController {
       ...(tools.length && { tools })
     }
 
-    // Archive todos FIRST so the trail msg sits right after the user prompt,
-    // not between thinking/tools and the final assistant text. Keeps the
-    // panel visually anchored where it lived during streaming.
-    const archived = archiveDoneTodos()
-    const body = hasDetails(finalDetails) ? [...segments, finalDetails] : segments
-    const finalMessages: Msg[] = [...archived, ...body]
+    // Archive prepended so the trail msg anchors under the user prompt,
+    // not between thinking/tools and final assistant text.
+    const finalMessages: Msg[] = [
+      ...archiveDoneTodos(),
+      ...segments,
+      ...(hasDetails(finalDetails) ? [finalDetails] : [])
+    ]
 
     if (finalText) {
       finalMessages.push({ role: 'assistant', text: finalText })