Hub toolbar URL tracking for iframe navigation (flakes-dya3)

The ingress hub page toolbar should display the current URL of the active iframe as the user navigates within it. Current implementation uses same-origin proxy (/s//) + setInterval polling but it’s not working reliably.

Context

The hub page (mixins/nixos/container/ingress.nix) embeds services in iframes. The toolbar at the top should show the current URL of the iframe content.

Current approach (not working)

1. Caddy proxy routes: handle_path /s/<port>/* in hub config proxies to localhost:<port>, making iframe same-origin
2. Iframe src uses /s/<port>/ instead of cross-origin http://<port>.yolo.incus
3. setInterval polls frame.contentWindow.location every 500ms
4. Translates proxy path back to real service URL for display

Known issues

• Apps with absolute paths (e.g. <a href="/dashboard">) break under path-based proxy — the iframe navigates to /dashboard on the hub domain instead of /s/<port>/dashboard, which 404s
• The proxy routes are generated dynamically by generate-ingress-config (needs ingress-sync after rebuild)
• Needs investigation: may need to verify Caddy config is actually being regenerated with the HUB_ROUTES

Alternative approaches to consider

• Inject postMessage script via response body rewriting (complex, no native Caddy support)
• Use a sub-path rewriting middleware or Caddy plugin
• Accept cross-origin limitation and only show base URL (simplest)
• Proxy all traffic through the Python sync API server (single-threaded bottleneck)

Files

• mixins/nixos/container/ingress.nix — hub HTML, Caddy config generation, Python API server