Connect a place search to a weather forecast (/umbrella/)

Agent concept
-------------
Chained tools: geocode -> forecast. The page shows the exact request URL and
trimmed JSON at each step, then a local yes/no/maybe rule. The page plays the
agent's part with a fixed script; no AI model runs here.

Network boundary
----------------
Live calls leave the visitor's browser only:
  - https://geocoding-api.open-meteo.com/v1/search
  - https://api.open-meteo.com/v1/forecast

No server proxy. CSP allows only those Open-Meteo hosts (plus 'self').

Saved example
-------------
If the API is blocked or fails, /umbrella/saved-example.json still completes the
lesson. The page shows: "Showing a saved example."

Class-mode check
----------------
node scripts/umbrella-class-mode.mjs
Logs to docs/umbrella-class-mode-log.txt (30 geocode+forecast pairs / 60s).

Credits
-------
Weather data by Open-Meteo, CC BY 4.0.
  https://open-meteo.com/
  https://creativecommons.org/licenses/by/4.0/
See LICENSE.txt on this path.