chore: Project cleanup and Canvas UX improvements (Phase 7-9)

## Cleanup (v0.5.0)
- Delete 102+ orphaned MCP session temp files
- Remove build artifacts (htmlcov, dist, __pycache__)
- Archive superseded plan docs (RALPH_LOOP V2/V3, CANVAS V3, etc.)
- Move debug/analysis scripts from tests/ to tools/analysis/
- Archive redundant NX journals to archive/nx_journals/
- Archive monolithic PROTOCOL.md to docs/archive/
- Update .gitignore with missing patterns
- Clean old study files (optimization_log_old.txt, run_optimization_old.py)

## Canvas UX (Phases 7-9)
- Phase 7: Resizable panels with localStorage persistence
  - Left sidebar: 200-400px, Right panel: 280-600px
  - New useResizablePanel hook and ResizeHandle component
- Phase 8: Enable all palette items
  - All 8 node types now draggable
  - Singleton logic for model/solver/algorithm/surrogate
- Phase 9: Solver configuration
  - Add SolverEngine type (nxnastran, mscnastran, python, etc.)
  - Add NastranSolutionType (SOL101-SOL200)
  - Engine/solution dropdowns in config panel
  - Python script path support

## Documentation
- Update CHANGELOG.md with recent versions
- Update docs/00_INDEX.md
- Create examples/README.md
- Add docs/plans/CANVAS_UX_IMPROVEMENTS.md

atomizer-dashboard/frontend/src/pages/CanvasView.tsx

@@ -11,8 +11,10 @@ import { NodeConfigPanel } from '../components/canvas/panels/NodeConfigPanel';
 import { NodeConfigPanelV2 } from '../components/canvas/panels/NodeConfigPanelV2';
 import { ChatPanel } from '../components/canvas/panels/ChatPanel';
 import { PanelContainer } from '../components/canvas/panels/PanelContainer';
+import { ResizeHandle } from '../components/canvas/ResizeHandle';
 import { useCanvasStore } from '../hooks/useCanvasStore';
 import { useSpecStore, useSpec, useSpecLoading, useSpecIsDirty, useSelectedNodeId } from '../hooks/useSpecStore';
+import { useResizablePanel } from '../hooks/useResizablePanel';
 // usePanelStore is now used by child components - PanelContainer handles panels
 import { useSpecUndoRedo, useUndoRedoKeyboard } from '../hooks/useSpecUndoRedo';
 import { useStudy } from '../context/StudyContext';
@@ -31,6 +33,23 @@ export function CanvasView() {
   const [paletteCollapsed, setPaletteCollapsed] = useState(false);
   const [leftSidebarTab, setLeftSidebarTab] = useState<'components' | 'files'>('components');
   const navigate = useNavigate();
+
+  // Resizable panels
+  const leftPanel = useResizablePanel({
+    storageKey: 'left-sidebar',
+    defaultWidth: 240,
+    minWidth: 200,
+    maxWidth: 400,
+    side: 'left',
+  });
+
+  const rightPanel = useResizablePanel({
+    storageKey: 'right-panel',
+    defaultWidth: 384,
+    minWidth: 280,
+    maxWidth: 600,
+    side: 'right',
+  });
   const [searchParams] = useSearchParams();
 
   // Spec mode is the default (AtomizerSpec v2.0)
@@ -423,7 +442,10 @@ export function CanvasView() {
       <main className="flex-1 overflow-hidden flex">
         {/* Left Sidebar with tabs (spec mode only - AtomizerCanvas has its own) */}
         {useSpecMode && (
-          <div className={`${paletteCollapsed ? 'w-14' : 'w-60'} bg-dark-850 border-r border-dark-700 flex flex-col transition-all duration-200`}>
+          <div 
+            className="relative bg-dark-850 border-r border-dark-700 flex flex-col"
+            style={{ width: paletteCollapsed ? 56 : leftPanel.width }}
+          >
             {/* Tab buttons (only show when expanded) */}
             {!paletteCollapsed && (
               <div className="flex border-b border-dark-700">
@@ -469,6 +491,16 @@ export function CanvasView() {
                 />
               )}
             </div>
+
+            {/* Resize handle (only when not collapsed) */}
+            {!paletteCollapsed && (
+              <ResizeHandle
+                onMouseDown={leftPanel.startDrag}
+                onDoubleClick={leftPanel.resetWidth}
+                isDragging={leftPanel.isDragging}
+                position="right"
+              />
+            )}
           </div>
         )}
 
@@ -494,14 +526,35 @@ export function CanvasView() {
         {/* Shows INSTEAD of chat when a node is selected */}
         {selectedNodeId ? (
           useSpecMode ? (
-            <NodeConfigPanelV2 onClose={() => useSpecStore.getState().clearSelection()} />
+            <div 
+              className="relative border-l border-dark-700 bg-dark-850 flex flex-col"
+              style={{ width: rightPanel.width }}
+            >
+              <ResizeHandle
+                onMouseDown={rightPanel.startDrag}
+                onDoubleClick={rightPanel.resetWidth}
+                isDragging={rightPanel.isDragging}
+                position="left"
+              />
+              <NodeConfigPanelV2 onClose={() => useSpecStore.getState().clearSelection()} />
+            </div>
           ) : (
             <div className="w-80 border-l border-dark-700 bg-dark-850 overflow-y-auto">
               <NodeConfigPanel nodeId={selectedNodeId} />
             </div>
           )
         ) : showChat ? (
-          <div className="w-96 border-l border-dark-700 bg-dark-850 flex flex-col">
+          <div 
+            className="relative border-l border-dark-700 bg-dark-850 flex flex-col"
+            style={{ width: rightPanel.width }}
+          >
+            {/* Resize handle */}
+            <ResizeHandle
+              onMouseDown={rightPanel.startDrag}
+              onDoubleClick={rightPanel.resetWidth}
+              isDragging={rightPanel.isDragging}
+              position="left"
+            />
             {/* Chat Header */}
             <div className="flex items-center justify-between px-4 py-3 border-b border-dark-700">
               <div className="flex items-center gap-2">