feat: Add delete functionality for user-authored nodes

- Add DELETE /api/nodes/[id] endpoint for deleting nodes
- Verify user authentication and ownership before deletion
- Delete from ATproto (source of truth) first, then SurrealDB cache
- Add delete button in ThoughtGalaxy component for user's own nodes
- Add confirmation modal before deletion
- Fix Modal z-index to appear above node detail panel (zIndex: 1001)
- Fix RecordId encoding issue (strip angle brackets ⟨⟩ from IDs)
- Remove deleted node and associated links from local state
- Add comprehensive Magnitude tests for delete functionality

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

components/ThoughtGalaxy.tsx

@@ -7,7 +7,9 @@ import {
   Text,
 } from '@react-three/drei';
 import { Suspense, useEffect, useRef, useState } from 'react';
-import { Stack, Text as MantineText, Paper, Title, Box, CloseButton, Group, Anchor, useComputedColorScheme } from '@mantine/core';
+import { Stack, Text as MantineText, Paper, Title, Box, CloseButton, Group, Anchor, useComputedColorScheme, Button, Modal } from '@mantine/core';
+import { IconTrash } from '@tabler/icons-react';
+import { notifications } from '@mantine/notifications';
 import { useRouter, usePathname, useSearchParams } from 'next/navigation';
 import * as THREE from 'three';
 
@@ -96,6 +98,9 @@ export function ThoughtGalaxy() {
   const [links, setLinks] = useState<LinkData[]>([]);
   const [selectedNode, setSelectedNode] = useState<NodeData | null>(null);
   const [emptyMessage, setEmptyMessage] = useState<string | null>(null);
+  const [currentUserDid, setCurrentUserDid] = useState<string | null>(null);
+  const [isDeleting, setIsDeleting] = useState(false);
+  const [deleteConfirmOpen, setDeleteConfirmOpen] = useState(false);
   const cameraControlsRef = useRef<CameraControls>(null);
   const hasFitCamera = useRef(false);
   const hasFocusedNode = useRef<string | null>(null);
@@ -104,6 +109,28 @@ export function ThoughtGalaxy() {
   const selectedNodeId = searchParams.get('node');
   const targetUserDid = searchParams.get('user'); // For viewing someone else's galaxy
 
+  // Fetch current user's profile to get their DID
+  useEffect(() => {
+    async function fetchCurrentUser() {
+      try {
+        const response = await fetch('/api/user/profile', {
+          credentials: 'include',
+        });
+        if (response.ok) {
+          const data = await response.json();
+          setCurrentUserDid(data.did);
+        }
+      } catch (error) {
+        console.error('[ThoughtGalaxy] Error fetching current user:', error);
+      }
+    }
+
+    // Only fetch current user if we're viewing our own galaxy
+    if (!targetUserDid) {
+      fetchCurrentUser();
+    }
+  }, [targetUserDid]);
+
   // Fetch data from API on mount and poll for updates
   useEffect(() => {
     async function fetchData() {
@@ -290,6 +317,51 @@ export function ThoughtGalaxy() {
     router.replace(`${pathname}${newSearch ? `?${newSearch}` : ''}`, { scroll: false });
   };
 
+  // Handle deleting a node
+  const handleDeleteNode = async () => {
+    if (!selectedNode) return;
+
+    setIsDeleting(true);
+    setDeleteConfirmOpen(false);
+
+    try {
+      // Extract clean ID from SurrealDB RecordId format (removes angle brackets ⟨⟩)
+      const cleanId = String(selectedNode.id).replace(/[⟨⟩]/g, '');
+
+      const response = await fetch(`/api/nodes/${cleanId}`, {
+        method: 'DELETE',
+        credentials: 'include',
+      });
+
+      if (!response.ok) {
+        const errorData = await response.json();
+        throw new Error(errorData.error || 'Failed to delete node');
+      }
+
+      notifications.show({
+        title: 'Node deleted',
+        message: 'Node has been deleted from Bluesky and your galaxy',
+        color: 'green',
+      });
+
+      // Remove the node from local state
+      setNodes((prevNodes) => prevNodes.filter((n) => n.id !== selectedNode.id));
+      setLinks((prevLinks) => prevLinks.filter((l) => l.in !== selectedNode.id && l.out !== selectedNode.id));
+
+      // Close the modal
+      handleCloseModal();
+    } catch (error) {
+      console.error('[ThoughtGalaxy] Delete error:', error);
+      notifications.show({
+        title: 'Delete failed',
+        message: error instanceof Error ? error.message : 'Failed to delete node',
+        color: 'red',
+      });
+    } finally {
+      setIsDeleting(false);
+    }
+  };
+
   console.log('[ThoughtGalaxy] Rendering with', nodes.length, 'nodes and', linkLines.length, 'link lines');
 
   // Show message if no nodes are ready yet
@@ -360,15 +432,30 @@ export function ThoughtGalaxy() {
                 <Title order={2} style={{ margin: 0, marginBottom: '0.25rem' }}>
                   {selectedNode.title}
                 </Title>
-                <Anchor
-                  href={`https://bsky.app/profile/${selectedNode.user_did}/post/${selectedNode.atp_uri.split('/').pop()}`}
-                  target="_blank"
-                  rel="noopener noreferrer"
-                  size="sm"
-                  c="dimmed"
-                >
-                  View on Bluesky
-                </Anchor>
+                <Group gap="sm" mt="xs">
+                  <Anchor
+                    href={`https://bsky.app/profile/${selectedNode.user_did}/post/${selectedNode.atp_uri.split('/').pop()}`}
+                    target="_blank"
+                    rel="noopener noreferrer"
+                    size="sm"
+                    c="dimmed"
+                  >
+                    View on Bluesky
+                  </Anchor>
+                  {/* Show delete button only for user's own nodes */}
+                  {currentUserDid && selectedNode.user_did === currentUserDid && (
+                    <Button
+                      size="xs"
+                      variant="subtle"
+                      color="red"
+                      leftSection={<IconTrash size={14} />}
+                      onClick={() => setDeleteConfirmOpen(true)}
+                      loading={isDeleting}
+                    >
+                      Delete
+                    </Button>
+                  )}
+                </Group>
               </Box>
               <CloseButton
                 size="lg"
@@ -394,6 +481,43 @@ export function ThoughtGalaxy() {
         </Box>
       )}
 
+      {/* Delete confirmation modal */}
+      <Modal
+        opened={deleteConfirmOpen}
+        onClose={() => setDeleteConfirmOpen(false)}
+        title="Delete Node"
+        centered
+        zIndex={1001}
+      >
+        <Stack gap="md">
+          <MantineText>
+            Are you sure you want to delete this node? This will:
+          </MantineText>
+          <Stack gap="xs" ml="md">
+            <MantineText size="sm">• Remove the post from Bluesky</MantineText>
+            <MantineText size="sm">• Delete the node from your galaxy</MantineText>
+            <MantineText size="sm" fw={600} c="red">This action cannot be undone.</MantineText>
+          </Stack>
+          <Group justify="flex-end" gap="sm">
+            <Button
+              variant="subtle"
+              onClick={() => setDeleteConfirmOpen(false)}
+              disabled={isDeleting}
+            >
+              Cancel
+            </Button>
+            <Button
+              color="red"
+              onClick={handleDeleteNode}
+              loading={isDeleting}
+              leftSection={<IconTrash size={16} />}
+            >
+              Delete Permanently
+            </Button>
+          </Group>
+        </Stack>
+      </Modal>
+
       <Canvas
         camera={{ position: [0, 5, 10], fov: 60 }}
         style={{ width: '100%', height: '100%' }}