SW implementation done

openspec/changes/archive/2026-02-10-service-workers/proposal.md

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+## Why
+
+Improve page load performance (especially repeat visits) by caching key assets closer to the user and reducing unnecessary network requests.
+
+## What Changes
+
+- Add a Service Worker to the site so the browser can cache and serve core assets efficiently.
+- Pre-cache the critical shell (CSS, JS, fonts, icons) and use a runtime caching strategy for images and other large assets.
+- Ensure safe update behavior on deploy (new service worker activates and old caches are cleaned up).
+- Keep development experience predictable (service worker disabled or bypassed in dev by default).
+
+## Capabilities
+
+### New Capabilities
+
+- `service-worker-performance`: Provide a service worker-based caching strategy that improves perceived load time and reduces network usage on repeat visits, while ensuring safe updates on new deploys.
+
+### Modified Capabilities
+
+- (none)
+
+## Impact
+
+- Adds new client-side assets for the service worker (e.g., `sw.js`) and registration logic in the site layout.
+- Changes browser caching behavior; must avoid serving stale HTML indefinitely and ensure caches are versioned/invalidated on deploy.
+- Service workers require a secure context (HTTPS) in production; local dev behavior should be explicitly controlled to avoid confusing caching during iteration.
+