refactor(ai): move reasoning helpers and the Coach error resolver into their own files

The reasoning separation grew three files past their size ratchet. The Local
client's reasoning collector and the new separation helpers move to
local-reasoning.ts, the gateway client's thinking room and reply separation
become two private methods, and the Coach's error-code resolver moves out of
chat-bubble.tsx into coach-error-key.ts, still re-exported from
message-thread.tsx. Code motion apart from comments that said when a branch
was added rather than what it does. The baselines record the shorter files.

Refs #1276

src/components/insights/coach-panel/chat-bubble.tsx

@@ -9,7 +9,6 @@ import { cn } from "@/lib/utils";
 import { Button } from "@/components/ui/button";
 import { useTranslations } from "@/lib/i18n/context";
 import { useAuth } from "@/hooks/use-auth";
-import { DEMO_READ_ONLY_CODE } from "@/lib/demo-refusal";
 import {
   parseChartTokens,
   tokenToMetric,
@@ -40,89 +39,19 @@ import type {
 } from "@/lib/ai/coach/types";
 import { translateOrNull } from "@/lib/i18n/translate-code";
 import { InlineAction } from "@/components/ui/inline-action";
+import { errorCodeToI18nKey } from "./coach-error-key";
 
 /**
  * Per-message bubble renderer for the Coach thread, split out of
  * `message-thread.tsx` (v1.28.26 file-size split). Owns the user + assistant
  * `ChatBubble` (steps, accompanying charts, the action row from
  * `message-actions.tsx`, and the follow-up chips under the latest answer),
- * the typing indicator, the chart-token grounding selector, and the
- * error-code → i18n resolver. `message-thread.tsx` re-exports the
- * previously public names so external call sites are unchanged.
+ * the typing indicator and the chart-token grounding selector. The
+ * error-code → i18n resolver lives in `coach-error-key.ts`.
+ * `message-thread.tsx` re-exports the previously public names so external
+ * call sites are unchanged.
  */
 
-/**
- * v1.4.25 — map server-emitted error codes to specific Coach i18n
- * keys. The chat route distinguishes the daily user-quota
- * (`coach.budget.exceeded`, returned as a JSON 429) from the provider
- * rate-limit (`coach.provider.rate_limited`, streamed as an SSE error
- * frame). Both used to surface as the generic provider-unavailable
- * copy; we now route each to its dedicated translation so the user
- * understands whether the limit is on their side (reset at UTC
- * midnight) or transient on the provider side (retry in ~5 min).
- *
- * Exported so the resolver can be pinned by unit tests without
- * standing up the whole thread renderer.
- */
-export function errorCodeToI18nKey(code: string): string {
-  switch (code) {
-    case "coach.budget.exceeded":
-      return "insights.coach.dailyLimitBody";
-    case "coach.provider.rate_limited":
-      return "insights.coach.providerRateLimitBody";
-    case "coach.network":
-      // v1.4.43 — a dropped network is the user's local
-      // problem and needs a different next action ("come back online")
-      // than a provider failure ("try again in a moment"). Split out
-      // so the user sees the actionable copy in the offline branch.
-      return "insights.coach.errorNetwork";
-    case "coach.provider.credential_expired":
-      // v1.11.0 — the user's primary AI provider credential is dead
-      // (auth-class failure). The next action is "reconnect", not "try
-      // again later", so it carries its own copy pointing at Settings.
-      return "insights.coach.errorCredentialExpired";
-    case "coach.provider.none":
-      // v1.18.6 — no AI provider is configured anywhere, so "try again
-      // in a moment" is the wrong instruction (it will 422 forever). Send
-      // the user to guided setup with a one-line explainer + a Settings
-      // link rendered alongside the bubble copy.
-      return "insights.coach.errorNoProvider";
-    case "coach.provider.reasoning_only":
-      // #1276 — the model was reached and answered with its reasoning
-      // only, even after being asked once more. "Try again in a moment"
-      // would be the wrong advice; the copy names what happened.
-      return "insights.coach.errorReasoningOnly";
-    case "coach.provider.unavailable":
-    case "coach.provider.empty":
-    case "coach.stream":
-      return "insights.coach.errorProvider";
-    // v1.39 — the capability refusals (`meta.errorCode` on a 403/422/503
-    // before the stream opens). Each says what is off and who can change it.
-    case "consent.ai.required":
-      return "insights.coach.errorConsent";
-    case "ai.record.notPermitted":
-      return "insights.coach.errorNotPermitted";
-    case "ai.unavailable":
-      return "insights.coach.errorUnavailable";
-    case "ai.provider.none":
-      return "insights.coach.errorNoProvider";
-    case "module.disabled":
-      return "insights.coach.errorCoachOff";
-    // A demo deploy refuses every write, the chat POST included. That is
-    // the demo's nature, not an outage, and the line says so.
-    case DEMO_READ_ONLY_CODE:
-      return "insights.coach.errorDemo";
-    default:
-      // The operator switched the Coach (or all AI) off on this server.
-      if (code.startsWith("assistant.disabled.")) {
-        return "insights.coach.errorOperatorOff";
-      }
-      // Forward-compat: try `insights.coach.<code>` for codes that
-      // ship their own translation (e.g. legacy `errorProvider`).
-      return `insights.coach.${code}`;
-  }
-}
-
 /**
  * v1.22 — Coach accompanying charts, Phase 1: the renderer half.
  *

src/components/insights/coach-panel/coach-error-key.ts

@@ -0,0 +1,78 @@
+/**
+ * The Coach's error-code → i18n-key resolver, split out of `chat-bubble.tsx`
+ * (file-size split, code motion). The bubble renders the key; an unknown code
+ * falls back to the generic provider copy there.
+ */
+import { DEMO_READ_ONLY_CODE } from "@/lib/demo-refusal";
+
+/**
+ * Map server-emitted error codes to specific Coach i18n
+ * keys. The chat route distinguishes the daily user-quota
+ * (`coach.budget.exceeded`, returned as a JSON 429) from the provider
+ * rate-limit (`coach.provider.rate_limited`, streamed as an SSE error
+ * frame). Both used to surface as the generic provider-unavailable
+ * copy; we now route each to its dedicated translation so the user
+ * understands whether the limit is on their side (reset at UTC
+ * midnight) or transient on the provider side (retry in ~5 min).
+ *
+ * Exported so the resolver can be pinned by unit tests without
+ * standing up the whole thread renderer.
+ */
+export function errorCodeToI18nKey(code: string): string {
+  switch (code) {
+    case "coach.budget.exceeded":
+      return "insights.coach.dailyLimitBody";
+    case "coach.provider.rate_limited":
+      return "insights.coach.providerRateLimitBody";
+    case "coach.network":
+      // A dropped network is the user's local
+      // problem and needs a different next action ("come back online")
+      // than a provider failure ("try again in a moment"). Split out
+      // so the user sees the actionable copy in the offline branch.
+      return "insights.coach.errorNetwork";
+    case "coach.provider.credential_expired":
+      // The user's primary AI provider credential is dead
+      // (auth-class failure). The next action is "reconnect", not "try
+      // again later", so it carries its own copy pointing at Settings.
+      return "insights.coach.errorCredentialExpired";
+    case "coach.provider.none":
+      // No AI provider is configured anywhere, so "try again
+      // in a moment" is the wrong instruction (it will 422 forever). Send
+      // the user to guided setup with a one-line explainer + a Settings
+      // link rendered alongside the bubble copy.
+      return "insights.coach.errorNoProvider";
+    case "coach.provider.reasoning_only":
+      // #1276 — the model was reached and answered with its reasoning
+      // only, even after being asked once more. "Try again in a moment"
+      // would be the wrong advice; the copy names what happened.
+      return "insights.coach.errorReasoningOnly";
+    case "coach.provider.unavailable":
+    case "coach.provider.empty":
+    case "coach.stream":
+      return "insights.coach.errorProvider";
+    // The capability refusals (`meta.errorCode` on a 403/422/503
+    // before the stream opens). Each says what is off and who can change it.
+    case "consent.ai.required":
+      return "insights.coach.errorConsent";
+    case "ai.record.notPermitted":
+      return "insights.coach.errorNotPermitted";
+    case "ai.unavailable":
+      return "insights.coach.errorUnavailable";
+    case "ai.provider.none":
+      return "insights.coach.errorNoProvider";
+    case "module.disabled":
+      return "insights.coach.errorCoachOff";
+    // A demo deploy refuses every write, the chat POST included. That is
+    // the demo's nature, not an outage, and the line says so.
+    case DEMO_READ_ONLY_CODE:
+      return "insights.coach.errorDemo";
+    default:
+      // The operator switched the Coach (or all AI) off on this server.
+      if (code.startsWith("assistant.disabled.")) {
+        return "insights.coach.errorOperatorOff";
+      }
+      // Forward-compat: try `insights.coach.<code>` for codes that
+      // ship their own translation (e.g. legacy `errorProvider`).
+      return `insights.coach.${code}`;
+  }
+}

src/components/insights/coach-panel/message-thread.tsx

@@ -48,11 +48,8 @@ import { translateOrNull } from "@/lib/i18n/translate-code";
 // per-message actions live in `chat-bubble.tsx`, the read-aloud stack in
 // `read-aloud.tsx`. The previously public names re-export from here so
 // external call sites are unchanged.
-export {
-  TypingDots,
-  errorCodeToI18nKey,
-  selectCoachChartTokens,
-} from "./chat-bubble";
+export { TypingDots, selectCoachChartTokens } from "./chat-bubble";
+export { errorCodeToI18nKey } from "./coach-error-key";
 
 /**
  * v1.4.20 — message-thread renderer.