Improve operational UX, recovery flows, and action safety

Implement the approved UX review across Fleet, Betas, Library, deployments, and Settings. Add reviewed promotion and reconciliation plans, atomic queued-removal cancellation, recoverable beta drafts and launch inputs, accessible controls, and mobile improvements.

Validated with 473 tests, a clean typecheck, production build, and isolated desktop/mobile browser walkthroughs. Include the review and implementation coverage notes.

src/routes/api/deployments/[id]/cancel/+server.ts

@@ -0,0 +1,7 @@
+import { json } from '@sveltejs/kit';
+import { cancelRemoval } from '$lib/server/fleet/deployments.js';
+
+export function POST({ params }: { params: { id: string } }) {
+    if (!cancelRemoval(params.id)) return json({ error: 'Removal has already begun or this request is no longer waiting. Refresh to see its current state.' }, { status: 409 });
+    return json({ ok: true });
+}