feat: detect prompt-too-long errors and offer compact action

Closes #158

- Detect "Prompt is too long" in assistant text blocks in wsl_bridge
- Emit error line type instead of assistant for better visibility
- Emit compact-prompt event after the error line
- Render a compact-prompt line as an action button in the terminal
- Clicking the button sends /compact to the active session
- Add getLineClass/getLinePrefix tests for compact-prompt type

src/lib/components/Terminal.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
   import { claudeStore, type TerminalLine } from "$lib/stores/claude";
   import { afterUpdate, tick, onMount, onDestroy } from "svelte";
+  import { invoke } from "@tauri-apps/api/core";
 
   import ConversationTabs from "./ConversationTabs.svelte";
   import Markdown from "./Markdown.svelte";
@@ -95,6 +96,8 @@
         return "terminal-thinking";
       case "rate-limit":
         return "terminal-rate-limit";
+      case "compact-prompt":
+        return "terminal-compact-prompt";
       default:
         return "terminal-default";
     }
@@ -193,6 +196,11 @@
     }, 2000);
   }
 
+  async function handleCompact() {
+    if (!currentConversationId) return;
+    await invoke("send_prompt", { conversationId: currentConversationId, message: "/compact" });
+  }
+
   // Collapsible tool lines
   const TOOL_COLLAPSE_THRESHOLD = 60;
   let expandedToolLines: Record<string, boolean> = {};
@@ -283,7 +291,11 @@
             {#if line.toolName}
               <span class="terminal-tool-name mr-2">[{line.toolName}]</span>
             {/if}
-            {#if line.type === "assistant" || line.type === "user"}
+            {#if line.type === "compact-prompt"}
+              <button class="compact-action-btn" onclick={handleCompact}>
+                ⚡ Compact Conversation
+              </button>
+            {:else if line.type === "assistant" || line.type === "user"}
               <div class="message-content-wrapper">
                 <Markdown
                   content={maskPaths(line.content, hidePaths)}
@@ -370,6 +382,30 @@
     color: var(--terminal-rate-limit, #fb923c);
   }
 
+  .terminal-compact-prompt {
+    color: var(--text-secondary);
+  }
+
+  .compact-action-btn {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.4em;
+    background: var(--bg-secondary);
+    border: 1px solid var(--terminal-error, #f87171);
+    color: var(--terminal-error, #f87171);
+    padding: 0.3em 0.8em;
+    cursor: pointer;
+    border-radius: 4px;
+    font-size: 0.9em;
+    font-family: inherit;
+    transition: all 0.15s ease;
+  }
+
+  .compact-action-btn:hover {
+    background: color-mix(in srgb, var(--terminal-error, #f87171) 15%, transparent);
+    color: var(--terminal-error, #f87171);
+  }
+
   .terminal-default {
     color: var(--text-primary);
   }