fix: Fix galaxy node clicking and navigation bugs

This commit fixes two critical bugs in the galaxy navigation:

**Bug #1: Direct node URLs redirected to /chat**
- Updated AppStateMachine to recognize /galaxy/* paths (including query params) as galaxy state
- Changed line 55 from `pathname === '/galaxy'` to `pathname === '/galaxy' || pathname.startsWith('/galaxy/')`
- Changed line 89 to compare pathname instead of lastNavigatedPathRef to preserve query params

**Bug #2: Modal closed when clicking nodes**
- Refactored ThoughtGalaxy to use URL query params (?node=xxx) instead of route params (/galaxy/node:xxx)
- This prevents component unmounting when switching between nodes
- Deleted app/galaxy/[node-id]/page.tsx (no longer needed)
- Updated app/galaxy/page.tsx with documentation comment
- Modified ThoughtGalaxy to:
  - Use useSearchParams() hook
  - Get selectedNodeId from query params
  - Update URL with query params on node click (doesn't cause remount)
  - Clear query params when modal closes

**Testing:**
- Verified manually with Playwright MCP that /galaxy?node=xxx preserves query params
- Verified state machine correctly recognizes galaxy state
- Created comprehensive Playwright test suite in tests/playwright/galaxy.spec.ts

**Files changed:**
- components/AppStateMachine.tsx: Fixed state machine to handle /galaxy/* paths and preserve query params
- components/ThoughtGalaxy.tsx: Refactored to use query params instead of route params
- app/galaxy/page.tsx: Added documentation
- app/galaxy/[node-id]/page.tsx: Deleted (replaced with query param approach)
- tests/playwright/galaxy.spec.ts: Added comprehensive test suite

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

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

components/ThoughtGalaxy.tsx

@@ -8,7 +8,7 @@ import {
 } from '@react-three/drei';
 import { Suspense, useEffect, useRef, useState } from 'react';
 import { Stack, Text as MantineText, Paper, Title, Box, CloseButton, Group, Anchor } from '@mantine/core';
-import { useRouter, usePathname } from 'next/navigation';
+import { useRouter, usePathname, useSearchParams } from 'next/navigation';
 import * as THREE from 'three';
 
 // Define the shape of nodes and links from API
@@ -78,9 +78,10 @@ function Node({
 }
 
 // 2. The Main Scene Component
-export function ThoughtGalaxy({ focusNodeId }: { focusNodeId?: string } = {}) {
+export function ThoughtGalaxy() {
   const router = useRouter();
   const pathname = usePathname();
+  const searchParams = useSearchParams();
   const [nodes, setNodes] = useState<NodeData[]>([]);
   const [links, setLinks] = useState<LinkData[]>([]);
   const [selectedNode, setSelectedNode] = useState<NodeData | null>(null);
@@ -88,6 +89,9 @@ export function ThoughtGalaxy({ focusNodeId }: { focusNodeId?: string } = {}) {
   const hasFitCamera = useRef(false);
   const hasFocusedNode = useRef<string | null>(null);
 
+  // Get selectedNodeId from URL query params
+  const selectedNodeId = searchParams.get('node');
+
   // Fetch data from API on mount and poll for updates
   useEffect(() => {
     async function fetchData() {
@@ -166,7 +170,7 @@ export function ThoughtGalaxy({ focusNodeId }: { focusNodeId?: string } = {}) {
 
   // Fit camera when nodes change and we haven't fitted yet
   useEffect(() => {
-    if (!hasFitCamera.current && nodes.length > 0 && !focusNodeId) {
+    if (!hasFitCamera.current && nodes.length > 0 && !selectedNodeId) {
       // Only auto-fit if we're not focusing on a specific node
       // Try to fit after a short delay to ensure Canvas is ready
       const timer = setTimeout(() => {
@@ -174,20 +178,20 @@ export function ThoughtGalaxy({ focusNodeId }: { focusNodeId?: string } = {}) {
       }, 100);
       return () => clearTimeout(timer);
     }
-  }, [nodes, focusNodeId]);
+  }, [nodes, selectedNodeId]);
 
-  // Auto-focus on specific node if focusNodeId is provided
+  // Auto-focus on specific node if selectedNodeId is provided via query params
   useEffect(() => {
-    if (focusNodeId && nodes.length > 0) {
-      const focusNode = nodes.find((n) => n.id === focusNodeId);
+    if (selectedNodeId && nodes.length > 0) {
+      const focusNode = nodes.find((n) => n.id === selectedNodeId);
       if (focusNode) {
-        console.log('[ThoughtGalaxy] Focusing on node:', focusNodeId);
+        console.log('[ThoughtGalaxy] Focusing on node:', selectedNodeId);
 
-        // Always update selected node when focusNodeId changes (don't wait for camera ref)
+        // Always update selected node when selectedNodeId changes (don't wait for camera ref)
         setSelectedNode(focusNode);
 
         // Move camera if ref is available and we haven't focused this specific node yet
-        if (cameraControlsRef.current && (!hasFocusedNode.current || hasFocusedNode.current !== focusNodeId)) {
+        if (cameraControlsRef.current && (!hasFocusedNode.current || hasFocusedNode.current !== selectedNodeId)) {
           cameraControlsRef.current.setLookAt(
             focusNode.coords_3d[0],
             focusNode.coords_3d[1],
@@ -197,11 +201,18 @@ export function ThoughtGalaxy({ focusNodeId }: { focusNodeId?: string } = {}) {
             focusNode.coords_3d[2],
             hasFocusedNode.current ? true : false // Animate if not initial load
           );
-          hasFocusedNode.current = focusNodeId;
+          hasFocusedNode.current = selectedNodeId;
         }
+      } else {
+        // Node ID in URL doesn't exist in data, clear it
+        setSelectedNode(null);
       }
+    } else if (!selectedNodeId && selectedNode) {
+      // Query param was cleared but we still have a selected node in state, clear it
+      setSelectedNode(null);
+      hasFocusedNode.current = null;
     }
-  }, [focusNodeId, nodes]);
+  }, [selectedNodeId, nodes, selectedNode]);
 
   // Map links to node positions
   const linkLines = links
@@ -220,33 +231,44 @@ export function ThoughtGalaxy({ focusNodeId }: { focusNodeId?: string } = {}) {
 
   // Camera animation on node click
   const handleNodeClick = (node: NodeData) => {
-    const targetPath = `/galaxy/${encodeURIComponent(node.id)}`;
+    console.log('[ThoughtGalaxy] Node clicked:', node.id);
 
     // Set selected node immediately for responsive UI
     setSelectedNode(node);
 
-    // Only navigate if we're not already on this node's page
-    if (pathname !== targetPath) {
-      // Clear the focused node ref to ensure camera animates on next render
+    // Update URL with query param (this won't cause remount)
+    const params = new URLSearchParams(searchParams);
+    params.set('node', node.id);
+    router.replace(`${pathname}?${params.toString()}`, { scroll: false });
+
+    // Animate camera to node
+    if (cameraControlsRef.current) {
+      // Clear the focused node ref to ensure camera animates
       hasFocusedNode.current = null;
-      // Use replace instead of push to avoid page reload issues
-      router.replace(targetPath);
-    } else {
-      // Already on this page, just animate camera to node
-      if (cameraControlsRef.current) {
-        cameraControlsRef.current.setLookAt(
-          node.coords_3d[0],
-          node.coords_3d[1],
-          node.coords_3d[2] + 2,
-          node.coords_3d[0],
-          node.coords_3d[1],
-          node.coords_3d[2],
-          true // Animate
-        );
-      }
+      cameraControlsRef.current.setLookAt(
+        node.coords_3d[0],
+        node.coords_3d[1],
+        node.coords_3d[2] + 2,
+        node.coords_3d[0],
+        node.coords_3d[1],
+        node.coords_3d[2],
+        true // Animate
+      );
     }
   };
 
+  // Handle closing the modal
+  const handleCloseModal = () => {
+    console.log('[ThoughtGalaxy] Closing modal');
+    setSelectedNode(null);
+
+    // Remove node query param from URL
+    const params = new URLSearchParams(searchParams);
+    params.delete('node');
+    const newSearch = params.toString();
+    router.replace(`${pathname}${newSearch ? `?${newSearch}` : ''}`, { scroll: false });
+  };
+
   console.log('[ThoughtGalaxy] Rendering with', nodes.length, 'nodes and', linkLines.length, 'link lines');
 
   // Show message if no nodes are ready yet
@@ -297,7 +319,7 @@ export function ThoughtGalaxy({ focusNodeId }: { focusNodeId?: string } = {}) {
               </Box>
               <CloseButton
                 size="lg"
-                onClick={() => setSelectedNode(null)}
+                onClick={handleCloseModal}
                 aria-label="Close node details"
                 style={{ flexShrink: 0 }}
               />
@@ -342,7 +364,7 @@ export function ThoughtGalaxy({ focusNodeId }: { focusNodeId?: string } = {}) {
             <Node
               key={node.id}
               node={node}
-              isFocused={focusNodeId === node.id || selectedNode?.id === node.id}
+              isFocused={selectedNodeId === node.id || selectedNode?.id === node.id}
               onNodeClick={handleNodeClick}
             />
           ))}