refactor: replace flyout popups with full-height resizable drawer

Sentry-style drawer slides out from rail edge, fills viewport height.
Drag handle on right edge to resize (180-400px range).
No more tooltip-style popups that cause layout jitter.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/layout/Sidebar.tsx

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useRef, useState } from 'react'
+import { useCallback, useEffect, useRef, useState, type PointerEvent as ReactPointerEvent } from 'react'
 import { Link, useLocation } from 'react-router-dom'
 import type { LucideIcon } from 'lucide-react'
 import {
@@ -185,6 +185,33 @@ export function Sidebar() {
     if (flyoutTimeout.current) clearTimeout(flyoutTimeout.current)
   }
 
+  /* ── Drawer resize ───────────────────────────────── */
+
+  const [drawerWidth, setDrawerWidth] = useState(240)
+  const isResizing = useRef(false)
+
+  const handleResizeStart = (e: ReactPointerEvent) => {
+    e.preventDefault()
+    isResizing.current = true
+    const startX = e.clientX
+    const startWidth = drawerWidth
+
+    const onMove = (ev: globalThis.PointerEvent) => {
+      if (!isResizing.current) return
+      const newWidth = Math.max(180, Math.min(400, startWidth + (ev.clientX - startX)))
+      setDrawerWidth(newWidth)
+    }
+
+    const onUp = () => {
+      isResizing.current = false
+      document.removeEventListener('pointermove', onMove)
+      document.removeEventListener('pointerup', onUp)
+    }
+
+    document.addEventListener('pointermove', onMove)
+    document.addEventListener('pointerup', onUp)
+  }
+
   /* Close flyout on Escape */
   useEffect(() => {
     const handleKey = (e: KeyboardEvent) => {
@@ -247,45 +274,7 @@ export function Sidebar() {
           </span>
         </Link>
 
-        {/* Flyout panel (icon rail only) */}
-        {hasChildren && !sidebarPinned && flyoutIndex === key && (
-          <div
-            className="absolute left-full top-0 z-50 ml-1"
-            style={{
-              maxHeight: '70vh',
-              overflowY: 'auto',
-            }}
-            onMouseEnter={keepFlyout}
-            onMouseLeave={closeFlyout}
-          >
-            <div
-              className="w-[220px] rounded-lg p-2 animate-fade-in"
-              style={{
-                background: '#14161d',
-                border: '1px solid #1e2130',
-                boxShadow: '0 4px 12px rgba(0,0,0,0.3)',
-              }}
-            >
-              {item.children!.map(child => (
-                <Link
-                  key={child.href}
-                  to={child.href}
-                  className={cn(
-                    'flex items-center justify-between rounded-md px-3 py-2 text-[0.8125rem] transition-colors',
-                    isChildActive(child)
-                      ? 'bg-[rgba(34,211,238,0.10)] text-[#67e8f9]'
-                      : 'text-[#848b9b] hover:bg-[#191c25] hover:text-[#e2e5eb]'
-                  )}
-                >
-                  <span>{child.label}</span>
-                  {child.count !== undefined && (
-                    <span className="text-[0.6875rem] font-mono text-[#4f5666]">{child.count}</span>
-                  )}
-                </Link>
-              ))}
-            </div>
-          </div>
-        )}
+        {/* Flyout rendered as drawer below */}
       </div>
     )
   }
@@ -364,15 +353,12 @@ export function Sidebar() {
     )
   }
 
-  /* ── Flyout positioning: use data attribute for lookup ── */
+  /* ── Find active flyout group for drawer ── */
 
-  const renderRailItemWithRef = (item: NavEntry, key: string) => {
-    return (
-      <div key={key} data-flyout-key={key}>
-        {renderRailItem(item, key + '-inner')}
-      </div>
-    )
-  }
+  const activeFlyoutGroup = flyoutIndex && !sidebarPinned
+    ? railGroups.find((_, i) => `rail-${i}` === flyoutIndex) ||
+      footerItems.find((_, i) => `footer-${i}` === flyoutIndex)
+    : null
 
   /* ── Main render ──────────────────────────────────── */
 
@@ -419,40 +405,91 @@ export function Sidebar() {
 
   /* Icon Rail (default) — 5 grouped icons, Sentry-style */
   return (
-    <nav
-      ref={sidebarRef}
-      className="sidebar flex flex-col items-center h-full"
-      style={{ background: '#0f1118', borderRight: '1px solid #1e2130' }}
-      onWheel={handleWheel}
+    <div
+      className="flex h-full"
+      onMouseLeave={closeFlyout}
     >
-      {/* Grouped nav items */}
-      <div className="flex flex-col items-center w-full px-1.5 pt-3 space-y-1">
-        {railGroups.map((item, i) => (
-          <div key={`rail-${i}`} data-flyout-key={`rail-${i}`}>
-            {renderRailItem(item, `rail-${i}-inner`)}
-          </div>
-        ))}
-      </div>
+      {/* Rail */}
+      <nav
+        ref={sidebarRef}
+        className="sidebar flex flex-col items-center h-full shrink-0"
+        style={{ background: '#0f1118', borderRight: '1px solid #1e2130', width: '72px' }}
+        onWheel={handleWheel}
+      >
+        {/* Grouped nav items */}
+        <div className="flex flex-col items-center w-full px-1.5 pt-3 space-y-1">
+          {railGroups.map((item, i) => renderRailItem(item, `rail-${i}`))}
+        </div>
 
-      <div className="flex-1" />
+        <div className="flex-1" />
 
-      {/* Footer: Account + Pin */}
-      <div className="flex flex-col items-center w-full px-1.5 pb-5 pt-2 space-y-1" style={{ borderTop: '1px solid #1e2130' }}>
-        {footerItems.map((item, i) => (
-          <div key={`footer-${i}`} data-flyout-key={`footer-${i}`}>
-            {renderRailItem(item, `footer-${i}-inner`)}
-          </div>
-        ))}
-        <button
-          type="button"
-          onClick={toggleSidebarPinned}
-          className="flex flex-col items-center justify-center rounded-lg px-1 py-2 text-[#6b7280] hover:text-[#848b9b] transition-colors"
-          title="Pin sidebar"
+        {/* Footer: Account + Pin */}
+        <div className="flex flex-col items-center w-full px-1.5 pb-5 pt-2 space-y-1" style={{ borderTop: '1px solid #1e2130' }}>
+          {footerItems.map((item, i) => renderRailItem(item, `footer-${i}`))}
+          <button
+            type="button"
+            onClick={toggleSidebarPinned}
+            className="flex flex-col items-center justify-center rounded-lg px-1 py-2 text-[#6b7280] hover:text-[#848b9b] transition-colors"
+            title="Pin sidebar"
+          >
+            <Pin size={18} className="opacity-60 hover:opacity-85" />
+            <span className="mt-1 text-[0.5625rem] font-mono leading-tight">Pin</span>
+          </button>
+        </div>
+      </nav>
+
+      {/* Drawer panel — full height, resizable */}
+      {activeFlyoutGroup && activeFlyoutGroup.children && (
+        <div
+          className="flex h-full shrink-0"
+          onMouseEnter={keepFlyout}
+          style={{ width: drawerWidth }}
         >
-          <Pin size={18} className="opacity-60 hover:opacity-85" />
-          <span className="mt-1 text-[0.5625rem] font-mono leading-tight">Pin</span>
-        </button>
-      </div>
-    </nav>
+          <div
+            className="flex flex-col h-full flex-1 overflow-y-auto py-4 px-2"
+            style={{
+              background: '#0f1118',
+              borderRight: '1px solid #1e2130',
+              boxShadow: '4px 0 12px rgba(0,0,0,0.2)',
+            }}
+          >
+            {/* Drawer header */}
+            <div className="px-3 mb-3">
+              <h3 className="text-[0.6875rem] font-mono uppercase tracking-[0.12em] text-[#4f5666]">
+                {activeFlyoutGroup.label}
+              </h3>
+            </div>
+
+            {/* Drawer items */}
+            <div className="space-y-0.5 px-1">
+              {activeFlyoutGroup.children.map(child => (
+                <Link
+                  key={child.href}
+                  to={child.href}
+                  className={cn(
+                    'flex items-center justify-between rounded-md px-3 py-2 text-[0.8125rem] transition-colors',
+                    isChildActive(child)
+                      ? 'bg-[rgba(34,211,238,0.10)] text-[#67e8f9]'
+                      : 'text-[#848b9b] hover:bg-[#191c25] hover:text-[#e2e5eb]'
+                  )}
+                >
+                  <span>{child.label}</span>
+                  {child.count !== undefined && (
+                    <span className="text-[0.6875rem] font-mono text-[#4f5666]">{child.count}</span>
+                  )}
+                </Link>
+              ))}
+            </div>
+          </div>
+
+          {/* Resize handle */}
+          <div
+            className="w-1 cursor-col-resize hover:bg-[#22d3ee]/20 active:bg-[#22d3ee]/30 transition-colors shrink-0"
+            onPointerDown={handleResizeStart}
+            title="Drag to resize"
+          />
+        </div>
+      )}
+    </div>
   )
 }