feat(web/ui): consolidate dialogs, cards, and breakpoints (Pass 3)

- Unify modal/dialog system; .modal-* are now aliases of .dialog-*
- Migrate WorkspacesPage, start-tool-modal, merge-dialog, workspace-tools-panel to .dialog-*
- Add .card-sm/.card-md/.card-lg/.card-elevated/.card-borderless modifiers
- Apply card utilities across workspaces, projects, ssh-keys, workspace-detail, git-history
- Remove duplicated card-like background/border/padding from page CSS
- Remove 860px breakpoint; standardize on 767px/768px mobile split
- Add docs/development/ui-review-checklist.md
- Archive web-ui-spacing-typography-rework OpenSpec change

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

@@ -255,7 +255,7 @@ export const InstanceList = ({
 			) : (
 				<div className="instance-grid">
 					{instances.map((instance) => (
-						<div key={instance.id} className="instance-card">
+						<div key={instance.id} className="card card-md instance-card">
 							<LoadingOverlay
 								visible={busyInstanceId === instance.id}
 								label={busyLabel}

apps/web/src/components/features/tool/start-tool-modal.tsx

@@ -47,9 +47,9 @@ export function StartToolModal({
 	};
 
 	return (
-		<div className="modal-overlay" onClick={onClose}>
-			<div className="modal-content" onClick={(e) => e.stopPropagation()}>
-				<div className="modal-header">
+		<div className="dialog-overlay" onClick={onClose}>
+			<div className="dialog" onClick={(e) => e.stopPropagation()}>
+				<div className="dialog-header">
 					<h3>
 						<Icon name="play" size="sm" /> Start Tool on {workspace.name}
 					</h3>
@@ -57,7 +57,7 @@ export function StartToolModal({
 						<Icon name="cancel" size="sm" />
 					</button>
 				</div>
-				<form onSubmit={handleSubmit}>
+				<form onSubmit={handleSubmit} className="dialog-body">
 					<div className="form-group">
 						<label htmlFor="tool-type">Tool Type</label>
 						<select
@@ -90,7 +90,7 @@ export function StartToolModal({
 						/>
 					</div>
 					{error && <p className="form-error">{error}</p>}
-					<div className="form-actions">
+					<div className="dialog-actions">
 						<button
 							type="button"
 							className="btn btn-secondary"