front: pass ?preview=all through API calls

[simonmorley]

Frontend side of TIA drip-feed gating. Reads ?preview=all from the current URL and forwards it on outbound API requests.

Implementation

New previewParam() helper in src/api/client.ts:

• Reads window.location.search live (per request — SPA navigation flips visibility immediately)
• Returns 'all' iff the URL has ?preview=all, else null
• SSR-safe (typeof window check)

fetchEvents, fetchNetworks, fetchStats now include the param when present.

Depends on

slasher-infra/18 + slasher-api PR. Merge order: infra → api → front.

Test plan

• npm run build — zero TS errors
• Post-merge: slashr.dev shows 5 networks (no celestia), slashr.dev/?preview=all shows 6

[gemini-code-assist]

Code Review

This pull request introduces a previewParam helper to support gated networks by appending a preview query parameter to API requests in fetchEvents, fetchNetworks, and fetchStats. The review feedback highlights that this parameter should be applied to all relevant API functions for full coverage and notes that React hooks need to be updated to trigger re-fetches upon URL changes. Furthermore, using URLSearchParams is recommended for consistency and better maintainability compared to manual string concatenation.

[gemini-code-assist]

The previewParam helper is a good addition for handling gated content, but there are two significant issues with the current implementation:

1. Incomplete Coverage: This parameter is only being passed in fetchEvents, fetchNetworks, and fetchStats. However, many other functions in this file (such as fetchValidator, fetchLeaderboard, fetchChainData, fetchDelegations, and fetchHealthCheck) likely also need to support this parameter to ensure that gated networks are visible and functional across all views (e.g., when viewing a specific validator's profile on a gated network).
2. SPA Navigation & React Hooks: The PR description states that visibility flips "immediately" during SPA navigation. While the API client reads the URL live, the corresponding hooks (like useNetworks and useStats in src/hooks/) do not include the URL search parameters in their dependency arrays. Consequently, navigating to or from a ?preview=all URL within the SPA will not trigger a re-fetch, and the UI will not update until a manual refresh or a different state change occurs.

Consider applying this parameter to all relevant API calls and updating the hooks to react to URL search parameter changes.

[gemini-code-assist]

For better maintainability and consistency with the approach used in fetchEvents, consider using URLSearchParams to construct the query string instead of manual string concatenation.

Suggested change

	const pv = previewParam();
	const suffix = pv ? `?preview=${pv}` : '';
	const res = await fetch(`${BASE_URL}/v1/networks${suffix}`);
	const qs = new URLSearchParams();
	const pv = previewParam();
	if (pv) qs.set('preview', pv);
	const query = qs.toString();
	const res = await fetch(`${BASE_URL}/v1/networks${query ? `?${query}` : ''}`);

[gemini-code-assist]

For better maintainability and consistency with the approach used in fetchEvents, consider using URLSearchParams to construct the query string instead of manual string concatenation.

Suggested change

	const pv = previewParam();
	const suffix = pv ? `?preview=${pv}` : '';
	const res = await fetch(`${BASE_URL}/v1/stats${suffix}`);
	const qs = new URLSearchParams();
	const pv = previewParam();
	if (pv) qs.set('preview', pv);
	const query = qs.toString();
	const res = await fetch(`${BASE_URL}/v1/stats${query ? `?${query}` : ''}`);