fix: constrain dialog content to the viewport

- Add dynamic viewport bounds and scrollable body regions to dialogs and modals\n- Make tool-launch popups use the shared scrollable body pattern\n- Keep mobile sheets, action sheets, and notification popups scroll-contained\n- Restore the ProjectsPage test setup required for the frontend suite\n\nOpenSpec: fix-dialog-scroll-containment\nQuality gates: npm run typecheck, npm run lint, npm test (88 passed), npm run build

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

@@ -578,19 +578,23 @@ export const InstanceList = ({
 			{showCreate && (
 				<div className="dialog-overlay" role="dialog" aria-modal="true">
 					<div className="dialog">
-						<h2>Launch Tool</h2>
-						<CreateSessionForm
-							projects={[]}
-							repositories={[]}
-							toolTypes={toolTypes}
-							fixedProjectId={projectId}
-							fixedRepoId={repoId}
-							projectName={projectName}
-							repoName={repoName}
-							onSuccess={handleCreateSuccess}
-							onCancel={() => setShowCreate(false)}
-							submitLabel="Launch"
-						/>
+						<div className="dialog-header">
+							<h2>Launch Tool</h2>
+						</div>
+						<div className="dialog-body">
+							<CreateSessionForm
+								projects={[]}
+								repositories={[]}
+								toolTypes={toolTypes}
+								fixedProjectId={projectId}
+								fixedRepoId={repoId}
+								projectName={projectName}
+								repoName={repoName}
+								onSuccess={handleCreateSuccess}
+								onCancel={() => setShowCreate(false)}
+								submitLabel="Launch"
+							/>
+						</div>
 					</div>
 				</div>
 			)}