Fix offline query parameter handling in embed route

[Copilot]

Query parameters to the embed route (?trainType=c51&messages=["hello"]) fail in offline mode if the exact URL wasn't previously cached. Service worker performs literal cache key matching including query strings.

Changes

• Strip query parameters for navigation request caching: Cache keys normalized by removing query strings since HTML content is identical. JavaScript reads parameters from window.location.search at runtime.

• Extract createRequestWithoutQuery helper: Eliminates duplication between online caching and offline matching logic. Short-circuits when no query parameters exist.

const createRequestWithoutQuery = (request: Request): Request => {
  const url = new URL(request.url);
  if (!url.search) return request;
  url.search = '';
  return new Request(url.toString(), { /* preserve request properties */ });
};

// Online: cache without query params
cache.put(createRequestWithoutQuery(request), response);

// Offline: match without query params
caches.match(createRequestWithoutQuery(request));

Result: Visiting embed.html online enables embed.html?trainType=c51&messages=["test"] offline.

Original prompt

In offline mode, query parameters to the embed route do not work correctly if they weren't used online. We should be able to set the train type or messages while offline since there is no new assets being loaded/required.

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[Copilot]

Pull request overview

This PR fixes offline query parameter handling in the embed route by normalizing cache keys to exclude query parameters. Previously, visiting embed.html?trainType=c51 would fail offline if only embed.html was cached, despite the HTML content being identical.

Changes:

• Added createRequestWithoutQuery helper function to strip query parameters from Request objects
• Modified navigation request caching to store responses without query parameters
• Updated offline cache matching to search without query parameters