Fix sidecar pipe crash on state changes and show logged-in state in settings

The state callback in main_headless.py wrote events to stdout
synchronously, so an EINVAL on the Tauri sidecar pipe (Windows) bubbled
up through _set_state and tore down engine init and reload_engine. That
turned PUT /api/config into a "Failed to fetch" for the user. The print
is now pipe-safe and api_server isolates the chained callback so a
future misbehaving listener cannot break the engine state machine.

Settings also now persists remote.email on login and shows a "Logged in
as <email>" indicator with a Log out button when an auth_token is
present, instead of leaving the email/password fields blank on reload.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/components/Settings.svelte

@@ -44,6 +44,7 @@
   let byokApiKey = $state("");
   let managedEmail = $state("");
   let managedPassword = $state("");
+  let managedLoggedIn = $state(false);
   let autoCheckUpdates = $state(true);
 
   let isCloudMode = $derived(remoteMode === "managed" || remoteMode === "byok");
@@ -131,6 +132,8 @@
     remoteMode = cfg.remote.mode;
     remoteServerUrl = cfg.remote.server_url;
     byokApiKey = cfg.remote.byok_api_key ?? "";
+    managedEmail = cfg.remote.email ?? "";
+    managedLoggedIn = !!(cfg.remote.auth_token && cfg.remote.email);
     autoCheckUpdates = cfg.updates.auto_check;
   });
 
@@ -268,12 +271,29 @@
         server_url: remoteServerUrl || MANAGED_SERVER_URL,
       });
       loginMessage = "Logged in successfully!";
+      managedPassword = "";
+      managedLoggedIn = true;
+      await configStore.fetchConfig();
     } catch (err) {
       console.error("Login failed:", err);
       loginMessage = "Login failed. Check your email and password.";
     }
   }
 
+  async function handleManagedLogout() {
+    try {
+      await configStore.updateConfig({
+        remote: { auth_token: "", email: "" },
+      });
+      managedLoggedIn = false;
+      managedPassword = "";
+      loginMessage = "";
+    } catch (err) {
+      console.error("Logout failed:", err);
+      loginMessage = `Error: ${err}`;
+    }
+  }
+
   const CAPTION_SERVER = "https://caption.shadowdao.com";
 
   function generateRandomName(): string {
@@ -489,34 +509,44 @@
         {/if}
         {#if remoteMode === "managed"}
           <div class="managed-auth">
-            <div class="field">
-              <label for="managed-email">Email</label>
-              <input
-                id="managed-email"
-                type="email"
-                bind:value={managedEmail}
-                placeholder="email@example.com"
-              />
-            </div>
-            <div class="field">
-              <label for="managed-password">Password</label>
-              <input
-                id="managed-password"
-                type="password"
-                bind:value={managedPassword}
-              />
-            </div>
-            <div class="auth-buttons">
-              <button onclick={handleManagedLogin}>Login</button>
-            </div>
+            {#if managedLoggedIn}
+              <p style="font-size: 13px; margin: 0 0 8px;">
+                <span style="color: var(--accent-green, #4CAF50);">✓ Logged in</span>
+                as <strong>{managedEmail}</strong>
+              </p>
+              <div class="auth-buttons">
+                <button onclick={handleManagedLogout}>Log out</button>
+              </div>
+            {:else}
+              <div class="field">
+                <label for="managed-email">Email</label>
+                <input
+                  id="managed-email"
+                  type="email"
+                  bind:value={managedEmail}
+                  placeholder="email@example.com"
+                />
+              </div>
+              <div class="field">
+                <label for="managed-password">Password</label>
+                <input
+                  id="managed-password"
+                  type="password"
+                  bind:value={managedPassword}
+                />
+              </div>
+              <div class="auth-buttons">
+                <button onclick={handleManagedLogin}>Login</button>
+              </div>
+              <p style="font-size: 11px; color: var(--text-muted); margin-top: 8px;">
+                Don't have an account? <a href="https://transcribe.shadowdao.com/register.html" target="_blank" rel="noopener" style="color: var(--accent-blue);">Sign up here</a>
+              </p>
+            {/if}
             {#if loginMessage}
               <p style="font-size: 12px; margin-top: 6px; color: {loginMessage.startsWith('Logged') ? 'var(--accent-green, #4CAF50)' : 'var(--accent-red, #f44336)'};">
                 {loginMessage}
               </p>
             {/if}
-            <p style="font-size: 11px; color: var(--text-muted); margin-top: 8px;">
-              Don't have an account? <a href="https://transcribe.shadowdao.com/register.html" target="_blank" rel="noopener" style="color: var(--accent-blue);">Sign up here</a>
-            </p>
           </div>
         {/if}
       </section>

src/lib/stores/config.svelte.ts

@@ -65,6 +65,7 @@ export interface AppConfig {
     mode: string;
     server_url: string;
     auth_token: string;
+    email: string;
     byok_api_key: string;
     deepgram_model: string;
     language: string;
@@ -131,6 +132,7 @@ function getDefaultConfig(): AppConfig {
       mode: "byok",
       server_url: "",
       auth_token: "",
+      email: "",
       byok_api_key: "",
       deepgram_model: "nova-2",
       language: "en-US",