feat(ui): add pending/update toast state and shared floating-menu positioning

Toast gains a pending/update lifecycle so async actions can show a single
toast that transitions from in-progress to success/error, instead of
firing a new one. Select's floating-menu placement logic is extracted
into a shared helper so other dropdown-style components (MultiSelect)
can reuse it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/components/ui/Select.jsx

@@ -16,6 +16,7 @@
 
 import { useState, useRef, useEffect, Children, isValidElement } from 'react'
 import { createPortal } from 'react-dom'
+import { computeFloatingMenuPosition } from '@/lib/floatingMenuPosition'
 
 // Parse React <option> children into a flat [{value, label, disabled}] array
 function parseOptions(children) {
@@ -46,7 +47,7 @@ export default function Select({
   ...props
 }) {
   const [open, setOpen]       = useState(false)
-  const [menuPos, setMenuPos] = useState({ top: 0, left: 0, width: 0 })
+  const [menuPos, setMenuPos] = useState({ top: 0, left: 0, width: 0, maxHeight: 280 })
   const triggerRef            = useRef(null)
   const menuRef               = useRef(null)
 
@@ -105,8 +106,7 @@ export default function Select({
   function openMenu() {
     if (disabled) return
     if (triggerRef.current) {
-      const r = triggerRef.current.getBoundingClientRect()
+      setMenuPos(computeFloatingMenuPosition(triggerRef.current.getBoundingClientRect()))
-      setMenuPos({ top: r.bottom + 4, left: r.left, width: r.width })
     }
     setOpen(true)
   }
@@ -130,7 +130,7 @@ export default function Select({
     <div
       ref={menuRef}
       className="select-menu"
-      style={{ top: menuPos.top, left: menuPos.left, width: menuPos.width }}
+      style={{ top: menuPos.top, bottom: menuPos.bottom, left: menuPos.left, width: menuPos.width, maxHeight: menuPos.maxHeight }}
       role="listbox"
       aria-label="Options"
     >

frontend/src/components/ui/Toast.jsx

@@ -12,8 +12,9 @@
 // Each toast auto-dismisses after `duration` ms (default 4000).
 // ToastProvider renders the stack itself via a portal — no extra component needed.
 
-import { createContext, useContext, useState, useCallback, useRef } from 'react'
+import { createContext, useContext, useState, useCallback, useRef, useEffect } from 'react'
 import { createPortal } from 'react-dom'
+import Spinner from '@/components/ui/Spinner'
 
 // ---------------------------------------------------------------------------
 // Context
@@ -49,7 +50,7 @@ function ToastIcon({ variant }) {
 // ---------------------------------------------------------------------------
 // Single Toast item
 // ---------------------------------------------------------------------------
-function ToastItem({ id, variant = 'info', title, message, duration = 4000, onDismiss }) {
+function ToastItem({ id, variant = 'info', title, message, duration = 4000, pending = false, onDismiss }) {
   const [exiting, setExiting] = useState(false)
 
   const dismiss = useCallback(() => {
@@ -57,15 +58,21 @@ function ToastItem({ id, variant = 'info', title, message, duration = 4000, onDi
     setTimeout(() => onDismiss(id), 300)
   }, [id, onDismiss])
 
-  // Auto-dismiss timer
+  // Auto-dismiss timer — does not run while `pending` (e.g. waiting on a command reply)
   const timerRef = useRef(null)
   const startTimer = () => {
+    if (pending) return
     timerRef.current = setTimeout(dismiss, duration)
   }
   const clearTimer = () => clearTimeout(timerRef.current)
 
-  // Start timer on mount
+  // (Re)start the timer whenever `pending` resolves to false, or on mount if already resolved
-  useState(() => { startTimer() })
+  useEffect(() => {
+    clearTimer()
+    startTimer()
+    return clearTimer
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [pending, duration])
 
   return (
     <div
@@ -76,7 +83,7 @@ function ToastItem({ id, variant = 'info', title, message, duration = 4000, onDi
       onMouseLeave={startTimer}
     >
       <div className="toast-icon">
-        <ToastIcon variant={variant} />
+        {pending ? <Spinner size="sm" /> : <ToastIcon variant={variant} />}
       </div>
 
       <div className="toast-content">
@@ -94,11 +101,13 @@ function ToastItem({ id, variant = 'info', title, message, duration = 4000, onDi
         </svg>
       </button>
 
-      {/* Progress bar — shrinks over duration */}
+      {/* Progress bar — shrinks over duration. Hidden while pending (no timeout running). */}
+      {!pending && (
         <div
           className="toast-progress"
           style={{ animationDuration: `${duration}ms` }}
         />
+      )}
     </div>
   )
 }
@@ -111,9 +120,9 @@ let _nextId = 1
 export function ToastProvider({ children }) {
   const [toasts, setToasts] = useState([])
 
-  const addToast = useCallback((variant, title, message, duration) => {
+  const addToast = useCallback((variant, title, message, duration, pending = false) => {
     const id = _nextId++
-    setToasts((prev) => [...prev, { id, variant, title, message, duration }])
+    setToasts((prev) => [...prev, { id, variant, title, message, duration, pending }])
     return id
   }, [])
 
@@ -121,11 +130,20 @@ export function ToastProvider({ children }) {
     setToasts((prev) => prev.filter((t) => t.id !== id))
   }, [])
 
+  // Update an existing toast in place — e.g. flip a `pending` (blue) toast to
+  // success/danger/warning once a command reply (or timeout) arrives.
+  const update = useCallback((id, patch) => {
+    setToasts((prev) => prev.map((t) => (t.id === id ? { ...t, ...patch } : t)))
+  }, [])
+
   const toast = {
     success: (title, message, duration) => addToast('success', title, message, duration),
     danger:  (title, message, duration) => addToast('danger',  title, message, duration),
     warning: (title, message, duration) => addToast('warning', title, message, duration),
     info:    (title, message, duration) => addToast('info',    title, message, duration),
+    // pending: creates a toast with no auto-dismiss timer until update() clears `pending`
+    pending: (title, message) => addToast('info', title, message, 4000, true),
+    update,
     dismiss,
   }
 

frontend/src/lib/floatingMenuPosition.js

@@ -0,0 +1,32 @@
+// frontend/src/lib/floatingMenuPosition.js
+// Positions a fixed-position dropdown menu relative to its trigger, flipping
+// above the trigger and clamping its height when there isn't enough room
+// below in the viewport (e.g. a Select near the bottom of the screen).
+//
+// Used by Select.jsx and MultiSelect.jsx — both render their menu via
+// createPortal(..., document.body) with position: fixed, so they need to
+// account for viewport edges themselves (page scroll doesn't move a
+// position:fixed element into view).
+
+const MENU_GAP = 4
+const MENU_MARGIN = 8 // minimum breathing room from the viewport edge
+const PREFERRED_MAX_HEIGHT = 280 // matches .select-menu's CSS max-height
+
+export function computeFloatingMenuPosition(triggerRect) {
+  const spaceBelow = window.innerHeight - triggerRect.bottom - MENU_GAP - MENU_MARGIN
+  const spaceAbove = triggerRect.top - MENU_GAP - MENU_MARGIN
+
+  // Prefer opening below; flip above only when below doesn't fit but above has more room.
+  const openAbove = spaceBelow < PREFERRED_MAX_HEIGHT && spaceAbove > spaceBelow
+
+  const maxHeight = Math.max(120, Math.min(PREFERRED_MAX_HEIGHT, openAbove ? spaceAbove : spaceBelow))
+
+  return {
+    left: triggerRect.left,
+    width: triggerRect.width,
+    maxHeight,
+    ...(openAbove
+      ? { bottom: window.innerHeight - triggerRect.top + MENU_GAP }
+      : { top: triggerRect.bottom + MENU_GAP }),
+  }
+}