feat(diagnostic): B1a-2 — Schalter fuer lokales LLM (Master/Nur-lokal/Tool-Umfang)

Neuer Settings-Block "Lokales LLM (schnelle Antworten)":
- Master-Checkbox "Lokales LLM nutzen" (aus = alles Claude)
- "Nur lokales LLM (kein Claude-Fallback)" — Eval-Haken
- "Tool-Umfang: Abgespeckt / Voll" — Voll deaktiviert (gated) + ⓘ mit VRAM-Erklaerung
- ⓘ-Haupt-Info erklaert Router/Latenz/Heim-Internet-Abhaengigkeit

server.js: GET/POST /api/local-llm-config <-> /shared/config/local_llm.json
(read/write, spiegelt runtime-config-Muster). Genau die Datei, die router.py
im Brain live liest. Onchange-Autosave, Status-Zeile, Laden bei ws.onopen.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

diagnostic/server.js

@@ -297,6 +297,35 @@ function writeRuntimeConfig(patch) {
 }
 
 // Atomic write: temp-file + rename, laute Logs bei Fehler.
+
+// ── Local-LLM-Config: /shared/config/local_llm.json ─────────────────
+// Der Router im Brain (router.py) liest diese Datei pro Request. Wir schreiben
+// sie hier aus den Diagnostic-Schaltern. Default = alles aus (nur Claude).
+const LOCAL_LLM_CONFIG_FILE = "/shared/config/local_llm.json";
+function readLocalLlmConfig() {
+  try {
+    const p = JSON.parse(fs.readFileSync(LOCAL_LLM_CONFIG_FILE, "utf-8"));
+    return {
+      enabled: !!p.enabled,
+      localOnly: !!p.localOnly,
+      toolVariant: p.toolVariant === "full" ? "full" : "slim",
+    };
+  } catch {
+    return { enabled: false, localOnly: false, toolVariant: "slim" };
+  }
+}
+function writeLocalLlmConfig(patch) {
+  const cur = readLocalLlmConfig();
+  if (typeof patch.enabled === "boolean") cur.enabled = patch.enabled;
+  if (typeof patch.localOnly === "boolean") cur.localOnly = patch.localOnly;
+  if (patch.toolVariant === "slim" || patch.toolVariant === "full") cur.toolVariant = patch.toolVariant;
+  fs.mkdirSync("/shared/config", { recursive: true });
+  const tmp = LOCAL_LLM_CONFIG_FILE + ".tmp";
+  fs.writeFileSync(tmp, JSON.stringify(cur, null, 2));
+  fs.renameSync(tmp, LOCAL_LLM_CONFIG_FILE);
+  return cur;
+}
+
 // ── File-Project-Manifest ───────────────────────────────────────────
 // Jeder Eintrag map[absoluter_pfad] = project_id (leer = Hauptchat).
 // Wird vom files-list-Endpoint + files-set-project gepflegt.
@@ -1573,6 +1602,24 @@ const server = http.createServer((req, res) => {
       }
     });
     return;
+  } else if (req.url === "/api/local-llm-config" && req.method === "GET") {
+    res.writeHead(200, { "Content-Type": "application/json" });
+    res.end(JSON.stringify(readLocalLlmConfig()));
+  } else if (req.url === "/api/local-llm-config" && req.method === "POST") {
+    let body = "";
+    req.on("data", chunk => { body += chunk; if (body.length > 8192) req.destroy(); });
+    req.on("end", () => {
+      try {
+        const cfg = writeLocalLlmConfig(JSON.parse(body));
+        res.writeHead(200, { "Content-Type": "application/json" });
+        res.end(JSON.stringify({ ok: true, config: cfg }));
+        log("info", "server", `Local-LLM-Config: enabled=${cfg.enabled} localOnly=${cfg.localOnly} tools=${cfg.toolVariant}`);
+      } catch (err) {
+        res.writeHead(400, { "Content-Type": "application/json" });
+        res.end(JSON.stringify({ ok: false, error: err.message }));
+      }
+    });
+    return;
   } else if (req.url === "/api/onboarding") {
     // RVS-Credentials fuer QR-Code App-Onboarding
     res.writeHead(200, { "Content-Type": "application/json" });