feat: busy container overlays for lifecycle actions

Add a reusable LoadingOverlay component that dims and disables the
container owning an in-flight action, with a spinning indicator and
label. Apply it to:

- SessionCard (when actionBusyId matches)
- InstanceList cards (per busyInstanceId with action-specific labels)
- CreateSessionForm (while submitting)
- ToolStarter (while starting)

Also add .icon-spin animation and position:relative to the relevant
containers.

Quality gates: npm run typecheck, npm run lint, npm test -- --run
(87 passed).

apps/web/src/components/features/session/create-session-form.tsx

@@ -1,5 +1,6 @@
 import { useState, useEffect } from "react";
 import { Icon } from "../../icon";
+import { LoadingOverlay } from "../../loading-overlay";
 import {
 	createInstance,
 	startInstance,
@@ -215,6 +216,7 @@ export const CreateSessionForm = ({
 
 	return (
 		<div className={`create-session-form-wrapper ${className}`}>
+			<LoadingOverlay visible={isSubmitting} label="Creating session..." />
 			<form onSubmit={handleSubmit} className="stack create-session-form">
 				{/* Project */}
 				<div className="form-field">

apps/web/src/components/features/session/session-card.tsx

@@ -3,6 +3,7 @@ import type { Session } from "../../../api/sessions";
 import { Icon } from "../../icon";
 import { useMobileViewport } from "../../../hooks/use-mobile-viewport";
 import { MobileActionSheet } from "../mobile/mobile-action-sheet";
+import { LoadingOverlay } from "../../loading-overlay";
 import type { IconName } from "../../icon";
 
 export interface SessionCardProps {
@@ -14,6 +15,7 @@ export interface SessionCardProps {
 	onRecreateTunnel?: (session: Session) => void;
 	onRename?: (session: Session, newName: string) => void;
 	isBusy?: boolean;
+	busyLabel?: string;
 	tunnelHealth?: {
 		healthy: boolean;
 		container_status: string;
@@ -46,6 +48,7 @@ export function SessionCard({
 	onRecreateTunnel,
 	onRename,
 	isBusy = false,
+	busyLabel = "Working...",
 	tunnelHealth = null,
 }: SessionCardProps) {
 	const [showActionSheet, setShowActionSheet] = useState(false);
@@ -106,6 +109,7 @@ export function SessionCard({
 
 	return (
 		<article className="card session-card">
+			<LoadingOverlay visible={isBusy} label={busyLabel} />
 			<div className="session-card-content">
 				<div className="session-card-header">
 					<div className="session-card-title">

apps/web/src/components/features/tool/instance-list.tsx

@@ -1,6 +1,7 @@
 import { useCallback, useEffect, useState } from "react";
 import { useNavigate } from "react-router-dom";
 import { Icon } from "../../icon";
+import { LoadingOverlay } from "../../loading-overlay";
 import type { ToolInstance } from "../../../api/sessions";
 import {
 	deleteInstance,
@@ -60,6 +61,7 @@ export const InstanceList = ({
 
 	// Per-instance busy state for actions
 	const [busyInstanceId, setBusyInstanceId] = useState<string | null>(null);
+	const [busyLabel, setBusyLabel] = useState("Working...");
 
 	const loadInstances = useCallback(async () => {
 		setLoading(true);
@@ -135,6 +137,7 @@ export const InstanceList = ({
 		sshKeyIds?: string[],
 	) => {
 		setBusyInstanceId(instanceId);
+		setBusyLabel("Starting...");
 		try {
 			await startInstance(
 				projectId,
@@ -156,6 +159,7 @@ export const InstanceList = ({
 
 	const handleStop = async (instanceId: string) => {
 		setBusyInstanceId(instanceId);
+		setBusyLabel("Stopping...");
 		try {
 			await stopInstance(projectId, repoId, instanceId);
 			setStopConfirmId(null);
@@ -173,6 +177,7 @@ export const InstanceList = ({
 		sshKeyIds?: string[],
 	) => {
 		setBusyInstanceId(instanceId);
+		setBusyLabel("Restarting...");
 		try {
 			await restartInstance(
 				projectId,
@@ -195,6 +200,7 @@ export const InstanceList = ({
 	const handleDelete = async (instanceId: string) => {
 		if (!confirm("Are you sure you want to delete this instance?")) return;
 		setBusyInstanceId(instanceId);
+		setBusyLabel("Deleting...");
 		try {
 			await deleteInstance(projectId, repoId, instanceId);
 			// Update state immediately instead of reloading
@@ -250,6 +256,10 @@ export const InstanceList = ({
 				<div className="instance-grid">
 					{instances.map((instance) => (
 						<div key={instance.id} className="instance-card">
+							<LoadingOverlay
+								visible={busyInstanceId === instance.id}
+								label={busyLabel}
+							/>
 							<div className="instance-info">
 								<div className="instance-name">{instance.display_name}</div>
 								<div className="instance-meta">

apps/web/src/components/features/tool/tool-starter.tsx

@@ -2,6 +2,7 @@
 
 import { useState, useEffect, useCallback } from "react";
 import { Icon } from "../../icon";
+import { LoadingOverlay } from "../../loading-overlay";
 import { listToolTypes, type ToolType } from "../../../api/tool-types";
 import {
 	listConfigProfiles,
@@ -172,6 +173,7 @@ export function ToolStarter({
 
 	return (
 		<div className="tool-starter">
+			<LoadingOverlay visible={starting} label="Starting tool..." />
 			{/* Context header — read-only workspace info */}
 			<div className="tool-starter-context">
 				<div className="context-row">

apps/web/src/components/loading-overlay.tsx

@@ -0,0 +1,21 @@
+import { Icon } from "./icon";
+
+interface LoadingOverlayProps {
+	visible: boolean;
+	label?: string;
+}
+
+export function LoadingOverlay({ visible, label }: LoadingOverlayProps) {
+	if (!visible) return null;
+
+	return (
+		<div className="loading-overlay" aria-live="polite">
+			<div className="loading-overlay-content">
+				<Icon name="loading" size="lg" className="icon-spin" ariaLabel={label} />
+				{label && (
+					<span className="loading-overlay-label">{label}</span>
+				)}
+			</div>
+		</div>
+	);
+}