refactor: tidy conversation tool after simplify review

Post-implementation simplify pass (reuse + efficiency + comment cleanup),
no behavior change:
- Reuse the existing buildTurnUserContent helper for both lapUserMessage
  constructions (sync + async) instead of re-inlining the identical
  context-or-prompt branch.
- Compute the lap transcript once per path and reuse it for the assistant
  message, persisted state, and response content (was building the same
  string twice in each of the sync and async paths).
- Collapse `x ? x : y` framing ternaries to `x || y`.
- Drop spec-narration/WHAT comments; keep the genuine constraint comments
  (SDK last-user-message, numeric async progress, abort rethrow, and the
  formatStatus result.content requirement).

25/25 conversation unit tests, eslint, and typecheck pass.

Author: FallDownTheSystem

src/tools/conversation.js

@@ -110,12 +110,8 @@ function buildFramingText({ i, models, turn_prompt }) {
   const nextModel = i < total - 1 ? models[i + 1] : null;
 
   const order = models.join(', ');
-  const prevText = prevModel
-    ? prevModel
-    : 'no one (you open the round)';
-  const nextText = nextModel
-    ? nextModel
-    : 'no one (you close this round)';
+  const prevText = prevModel || 'no one (you open the round)';
+  const nextText = nextModel || 'no one (you close this round)';
   const handoffText = nextModel
     ? `Your response will be passed to the next participant (${nextModel}).`
     : 'Your response will be returned to the user, as you are the last participant this round.';
@@ -564,7 +560,6 @@ export async function conversationTool(args, dependencies) {
       }
     }
 
-    // Process context (files and images) attached to the lap user message
     const contextMessage = await buildContextMessage(
       files,
       images,
@@ -661,14 +656,16 @@ export async function conversationTool(args, dependencies) {
     // Build the lap user message (lap prompt, with context if present)
     const lapUserMessage = {
       role: 'user',
-      content: contextMessage?.content
-        ? [...contextMessage.content, { type: 'text', text: prompt }]
-        : prompt,
+      content: buildTurnUserContent(prompt, contextMessage),
     };
 
+    // Labeled lap transcript (### <model> (turn <n>):) — computed once and reused
+    // for the assistant message, the persisted state, and the response content.
+    const transcript = formatLapTranscript(lapTurns);
+
     const assistantMessage = {
       role: 'assistant',
-      content: formatLapTranscript(lapTurns),
+      content: transcript,
     };
 
     // Save conversation state (skip on abort to avoid persisting incomplete history)
@@ -721,10 +718,6 @@ export async function conversationTool(args, dependencies) {
 
     const continuationIdLine = `continuation_id: ${continuationId}\n\n`;
 
-    // Rendered lap transcript with labeled turns (### <model> (turn <n>):).
-    // Per spec requirement 11, the response content must include this transcript.
-    const transcript = formatLapTranscript(lapTurns);
-
     const result = {
       status: 'conversation_complete',
       content: transcript,
@@ -1046,14 +1039,16 @@ async function executeConversationWithStreaming(args, dependencies, context) {
 
   const lapUserMessage = {
     role: 'user',
-    content: contextMessage?.content
-      ? [...contextMessage.content, { type: 'text', text: prompt }]
-      : prompt,
+    content: buildTurnUserContent(prompt, contextMessage),
   };
 
+  // Final lap transcript — computed once and reused for the assistant message,
+  // the persisted state, and the returned top-level content.
+  const transcript = formatLapTranscript(lapTurns);
+
   const assistantMessage = {
     role: 'assistant',
-    content: formatLapTranscript(lapTurns),
+    content: transcript,
   };
 
   // Save conversation state
@@ -1114,11 +1109,11 @@ async function executeConversationWithStreaming(args, dependencies, context) {
 
   const messageCount = (conversationState?.messages || []).length;
 
-  // CRITICAL: top-level `content` is required so check_status renders the
-  // transcript on completion (formatStatus.js only shows result.content).
+  // Top-level `content` is required: formatStatus only renders result.content
+  // when displaying a completed async job.
   return {
     status: 'conversation_complete',
-    content: formatLapTranscript(lapTurns),
+    content: transcript,
     models_consulted: models.length,
     successful_turns: turnsSuccessful,
     failed_turns: turnsFailed,