feat: collapsible messages, German cost format, stats persistence [appimage]

- Long messages (>25 lines) auto-collapse with expand/collapse button
- Cost display uses German format: "16,23$" instead of "$16.230"
- Session stats (tokens, cost, count) persist to DB after each response
  via new update_session_stats command — survives app restart
- Small costs shown as cents (e.g. "3,2¢")

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/lib.rs

@@ -77,6 +77,7 @@ pub fn run() {
             session::resume_session,
             session::get_active_session,
             session::set_claude_session_id,
+            session::update_session_stats,
             // Messages
             db::save_message,
             db::load_messages,

src-tauri/src/session.rs

@@ -153,3 +153,30 @@ pub async fn set_claude_session_id(
 
     Ok(())
 }
+
+/// Aktualisiert nur die Statistiken einer Session (Token, Kosten, Message-Count)
+#[tauri::command]
+pub async fn update_session_stats(
+    app: AppHandle,
+    session_id: String,
+    token_input: i64,
+    token_output: i64,
+    cost_usd: f64,
+    message_count: i32,
+) -> Result<(), String> {
+    let state = app.state::<Arc<Mutex<db::Database>>>();
+    let db = state.lock().unwrap();
+    db.conn.execute(
+        "UPDATE sessions SET token_input = ?1, token_output = ?2, cost_usd = ?3,
+         message_count = ?4, updated_at = ?5 WHERE id = ?6",
+        rusqlite::params![
+            token_input,
+            token_output,
+            cost_usd,
+            message_count,
+            chrono::Utc::now().to_rfc3339(),
+            session_id,
+        ],
+    ).map_err(|e| e.to_string())?;
+    Ok(())
+}

src/lib/components/ChatPanel.svelte

@@ -23,6 +23,23 @@
 
 	marked.setOptions({ breaks: true, gfm: true, renderer });
 
+	// Collapse: Nachrichten mit > 25 Zeilen werden eingeklappt
+	const COLLAPSE_LINES = 25;
+	let expandedMessages = new Set<string>();
+
+	function toggleExpand(msgId: string) {
+		if (expandedMessages.has(msgId)) {
+			expandedMessages.delete(msgId);
+		} else {
+			expandedMessages.add(msgId);
+		}
+		expandedMessages = expandedMessages;
+	}
+
+	function shouldCollapse(content: string): boolean {
+		return content.split('\n').length > COLLAPSE_LINES;
+	}
+
 	function renderMarkdown(text: string): string {
 		try {
 			return marked.parse(text) as string;
@@ -831,7 +848,21 @@
 							</div>
 						{:else if message.role === 'assistant'}
 							{#if message.content}
-								{@html renderMarkdown(message.content)}
+								{#if shouldCollapse(message.content) && !expandedMessages.has(message.id)}
+									<div class="msg-collapsed">
+										{@html renderMarkdown(message.content.split('\n').slice(0, COLLAPSE_LINES).join('\n') + '\n...')}
+									</div>
+									<button class="expand-btn" onclick={() => toggleExpand(message.id)}>
+										▼ Mehr anzeigen ({message.content.split('\n').length} Zeilen)
+									</button>
+								{:else}
+									{@html renderMarkdown(message.content)}
+									{#if shouldCollapse(message.content)}
+										<button class="expand-btn" onclick={() => toggleExpand(message.id)}>
+											▲ Einklappen
+										</button>
+									{/if}
+								{/if}
 							{:else if $isProcessing}
 								<span class="typing">
 									<span class="dot"></span>
@@ -1270,6 +1301,29 @@
 		line-height: 1.6;
 	}
 
+	.msg-collapsed {
+		overflow: hidden;
+	}
+
+	.expand-btn {
+		display: block;
+		width: 100%;
+		padding: 0.35rem;
+		margin-top: 0.3rem;
+		background: var(--bg-tertiary, #2a2a2a);
+		border: 1px solid var(--border, #3a3a3a);
+		border-radius: 4px;
+		color: var(--accent, #6aa3ff);
+		font-size: 0.75rem;
+		cursor: pointer;
+		text-align: center;
+		transition: background 0.15s;
+	}
+
+	.expand-btn:hover {
+		background: var(--bg-hover, #333);
+	}
+
 	/* Markdown-Styles innerhalb von Nachrichten */
 	.message-content :global(p) {
 		margin: 0.3em 0;

src/lib/components/SessionList.svelte

@@ -126,7 +126,8 @@
 
 	function formatCost(usd: number): string {
 		if (usd === 0) return '';
-		return `$${usd.toFixed(3)}`;
+		if (usd < 0.01) return `${(usd * 100).toFixed(1)}¢`;
+		return `${usd.toFixed(2).replace('.', ',')}$`;
 	}
 </script>
 

src/lib/stores/events.ts

@@ -381,6 +381,19 @@ export async function initEventListeners(): Promise<void> {
 						outputTokens: tokens.output || 0,
 					}));
 				}
+
+				// Session-Stats in DB persistieren (überlebt App-Neustart)
+				const appSessionId = get(currentSessionId);
+				if (appSessionId) {
+					const stats = get(sessionStats);
+					invoke('update_session_stats', {
+						sessionId: appSessionId,
+						tokenInput: stats.totalTokensIn,
+						tokenOutput: stats.totalTokensOut,
+						costUsd: stats.totalCost,
+						messageCount: stats.messageCount,
+					}).catch((err: unknown) => console.warn('Session-Stats speichern fehlgeschlagen:', err));
+				}
 			}
 		})
 	);

src/routes/+layout.svelte

@@ -136,9 +136,9 @@
 	}
 
 	function formatCost(usd: number): string {
-		if (usd === 0) return '$0';
+		if (usd === 0) return '0$';
-		if (usd < 0.01) return `$${usd.toFixed(4)}`;
+		if (usd < 0.01) return `${(usd * 100).toFixed(1)}¢`;
-		return `$${usd.toFixed(2)}`;
+		return `${usd.toFixed(2).replace('.', ',')}$`;
 	}
 
 	function formatTokens(n: number): string {