feat: add clipboard history for code snippets

Implements issue #25 - Clipboard History feature that tracks copied
code snippets with language detection, search, and filtering.

Backend (Rust):
- New clipboard.rs module with persistent storage via tauri-plugin-store
- Commands: capture, list, delete, toggle pin, clear, search, update language
- Auto-deduplication and max history size (100 entries)
- Pinned entries stay at top and persist through clear

Frontend (Svelte/TypeScript):
- Clipboard store with filtering, search, and language detection
- ClipboardHistoryPanel component with search, language filter, pin/delete
- Clipboard button added to InputBar next to Snippets/Actions
- Auto-capture from code block copy buttons
- Auto-capture from manual text selection in terminal
- Insert snippets directly into input field

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/lib/components/Terminal.svelte

@@ -1,10 +1,11 @@
 <script lang="ts">
   import { claudeStore, type TerminalLine } from "$lib/stores/claude";
-  import { afterUpdate, tick } from "svelte";
+  import { afterUpdate, tick, onMount, onDestroy } from "svelte";
   import ConversationTabs from "./ConversationTabs.svelte";
   import Markdown from "./Markdown.svelte";
   import HighlightedText from "./HighlightedText.svelte";
   import { searchState, searchQuery } from "$lib/stores/search";
+  import { clipboardStore } from "$lib/stores/clipboard";
 
   let terminalElement: HTMLDivElement;
   let shouldAutoScroll = true;
@@ -122,6 +123,32 @@
       searchState.setMatchCount(0);
     }
   }
+
+  // Handle manual text selection copy events
+  function handleCopy() {
+    const selection = window.getSelection();
+    const selectedText = selection?.toString();
+
+    if (selectedText && selectedText.trim().length > 0) {
+      // Only capture multi-line or longer text (likely code/meaningful content)
+      if (selectedText.includes("\n") || selectedText.length > 50) {
+        clipboardStore.captureClipboard(selectedText, null, "Copied from chat");
+      }
+    }
+  }
+
+  onMount(() => {
+    // Listen for copy events on the terminal
+    if (terminalElement) {
+      terminalElement.addEventListener("copy", handleCopy);
+    }
+  });
+
+  onDestroy(() => {
+    if (terminalElement) {
+      terminalElement.removeEventListener("copy", handleCopy);
+    }
+  });
 </script>
 
 <div