feat: add native clipboard support for screenshot paste (#67)

## Summary
- Adds Tauri clipboard-manager plugin to read images from native clipboard
- Falls back to native clipboard when WebView clipboard API returns empty (fixes screenshot paste)
- Allows sending messages with just attachments (no text required)
- Logs attached files to output with 📎 emoji

## Test plan
- [ ] Build and run the app natively on Windows
- [ ] Copy a screenshot (Win+Shift+S) and paste in the chat input
- [ ] Verify the screenshot appears as an attachment preview
- [ ] Send the attachment and verify Claude receives the file path
- [ ] Test sending a message with only an attachment (no text)
- [ ] Verify the 📎 log line shows the attached filename

**Note:** Paste will not work in WSLg dev environment due to clipboard isolation - needs native Windows build to test.

✨ This PR was created with help from Hikari~ 🌸

Co-authored-by: Hikari <hikari@nhcarrigan.com>
Reviewed-on: #67
Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Co-committed-by: Naomi Carrigan <commits@nhcarrigan.com>

src/lib/stores/claude.ts

@@ -25,6 +25,7 @@ export const claudeStore = {
   isProcessing: conversationsStore.isProcessing,
   grantedTools: conversationsStore.grantedTools,
   pendingRetryMessage: conversationsStore.pendingRetryMessage,
+  attachments: conversationsStore.attachments,
 
   // New conversation-aware subscriptions
   conversations: conversationsStore.conversations,
@@ -67,6 +68,12 @@ export const claudeStore = {
   saveScrollPosition: conversationsStore.saveScrollPosition,
   getScrollPosition: conversationsStore.getScrollPosition,
 
+  // Attachment management
+  addAttachment: conversationsStore.addAttachment,
+  removeAttachment: conversationsStore.removeAttachment,
+  clearAttachments: conversationsStore.clearAttachments,
+  getAttachments: conversationsStore.getAttachments,
+
   getGrantedTools: (): string[] => {
     let tools: string[] = [];
     conversationsStore.grantedTools.subscribe((t) => (tools = Array.from(t)))();
@@ -86,6 +93,7 @@ export const claudeStore = {
     conversationsStore.setWorkingDirectory("");
     conversationsStore.setProcessing(false);
     conversationsStore.revokeAllTools();
+    conversationsStore.clearAttachments();
     // Also clear history restoration
     clearHistoryRestore();
   },

src/lib/stores/conversations.ts

@@ -4,6 +4,7 @@ import type {
   ConnectionStatus,
   PermissionRequest,
   UserQuestionEvent,
+  Attachment,
 } from "$lib/types/messages";
 import type { CharacterState } from "$lib/types/states";
 import { cleanupConversationTracking } from "$lib/tauri";
@@ -24,6 +25,7 @@ export interface Conversation {
   scrollPosition: number;
   createdAt: Date;
   lastActivityAt: Date;
+  attachments: Attachment[];
 }
 
 function createConversationsStore() {
@@ -59,6 +61,7 @@ function createConversationsStore() {
       scrollPosition: -1, // -1 means "scroll to bottom" (auto-scroll)
       createdAt: new Date(),
       lastActivityAt: new Date(),
+      attachments: [],
     };
   }
 
@@ -109,6 +112,7 @@ function createConversationsStore() {
   );
   const pendingQuestion = derived(activeConversation, ($conv) => $conv?.pendingQuestion || null);
   const scrollPosition = derived(activeConversation, ($conv) => $conv?.scrollPosition ?? -1);
+  const attachments = derived(activeConversation, ($conv) => $conv?.attachments || []);
 
   return {
     // Expose derived stores for compatibility
@@ -122,6 +126,7 @@ function createConversationsStore() {
     grantedTools: { subscribe: grantedTools.subscribe },
     pendingRetryMessage: { subscribe: pendingRetryMessage.subscribe },
     scrollPosition: { subscribe: scrollPosition.subscribe },
+    attachments: { subscribe: attachments.subscribe },
 
     // New conversation-specific stores
     conversations: { subscribe: conversations.subscribe },
@@ -272,7 +277,7 @@ function createConversationsStore() {
       return newConv.id;
     },
 
-    deleteConversation: (id: string) => {
+    deleteConversation: async (id: string) => {
       ensureInitialized();
       const convs = get(conversations);
       const activeId = get(activeConversationId);
@@ -282,8 +287,8 @@ function createConversationsStore() {
         return false;
       }
 
-      // Clean up tracking for this conversation
-      cleanupConversationTracking(id);
+      // Clean up tracking for this conversation (including temp files)
+      await cleanupConversationTracking(id);
 
       conversations.update((c) => {
         c.delete(id);
@@ -571,6 +576,58 @@ function createConversationsStore() {
       return conv?.grantedTools.has(toolName) || false;
     },
 
+    // Attachment management
+    addAttachment: (attachment: Attachment) => {
+      const activeId = get(activeConversationId);
+      if (!activeId) return;
+
+      conversations.update((convs) => {
+        const conv = convs.get(activeId);
+        if (conv) {
+          conv.attachments.push(attachment);
+          conv.lastActivityAt = new Date();
+        }
+        return convs;
+      });
+    },
+
+    removeAttachment: (id: string) => {
+      const activeId = get(activeConversationId);
+      if (!activeId) return;
+
+      conversations.update((convs) => {
+        const conv = convs.get(activeId);
+        if (conv) {
+          conv.attachments = conv.attachments.filter((a) => a.id !== id);
+          conv.lastActivityAt = new Date();
+        }
+        return convs;
+      });
+    },
+
+    clearAttachments: () => {
+      const activeId = get(activeConversationId);
+      if (!activeId) return;
+
+      conversations.update((convs) => {
+        const conv = convs.get(activeId);
+        if (conv) {
+          conv.attachments = [];
+          conv.lastActivityAt = new Date();
+        }
+        return convs;
+      });
+    },
+
+    getAttachments: (): Attachment[] => {
+      const activeId = get(activeConversationId);
+      if (!activeId) return [];
+
+      const convs = get(conversations);
+      const conv = convs.get(activeId);
+      return conv?.attachments || [];
+    },
+
     // Add initialization helper
     initialize: () => {
       ensureInitialized();