feat(coach): seams for steps, tables, charts, method, chips and clarification

Each later piece of the dialog gets its own module, answering nothing for
now: the step builder, the table projection and chart choice, the result
ref marks, the follow-up derivation, sentinel, resolution and continue
chip, the reuse turn, the clarification parse and answer, the method line,
and the four prompt addenda. The turn pipeline calls them where they
belong, so the frames go out in the documented order (step, token,
provenance, result, cards, clarification, followUps, done) and a blocked
turn drops its tables, chips and clarification. With every piece empty
the stream and the prompt stay byte for byte as before.

src/app/api/insights/chat/route.ts

@@ -109,6 +109,8 @@ async function handleChatRequest(request: NextRequest): Promise<Response> {
     scope,
     guidedQuestion,
     workoutId,
+    followUp,
+    clarification,
   } = parsed.data;
 
   // Per-user request-rate ceiling layered in front of the daily budget
@@ -171,6 +173,8 @@ async function handleChatRequest(request: NextRequest): Promise<Response> {
     scope,
     guidedQuestion,
     workoutId,
+    followUp,
+    clarification,
     recheckCapability: coachCapabilityRefusal,
   });
 }