docs: add wallet provider migration guide for Base App WebView (2026)

[schoolkamsergj]

Summary

Adds a new technical guide covering the breaking wallet provider change introduced by Base App's April 2026 update.

Base App now opens mini-apps in a standard WebView instead of a Farcaster mini-app host. This causes sdk.wallet.getEthereumProvider() to hang indefinitely — no error, no timeout — breaking any mini-app that relies on the SDK for wallet access.

This guide documents the issue and provides a working detection + fallback pattern.

What's added

docs/apps/technical-guides/wallet-provider-base-app-webview-2026.mdx

• Detection pattern using sdk.isInMiniApp() to distinguish Base App WebView from true Farcaster embed (Warpcast)
• Fallback to injected EIP-1193 (window.ethereum / window.coinbaseWalletExtension) for Base App WebView context
• Comparison table: which SDK calls work vs hang in Base App WebView
• Full wagmi example with farcasterMiniApp() + injected() connectors and auto-connect hook

Context

Discovered while building a mini-app on Base mainnet. The app silently hung on every transaction when opened via Base App — no console error, no rejection, just an indefinite loading state. Root cause: sdk.isInMiniApp() returns false in Base App WebView, so the Farcaster host is never present.

Fixes #1420

Tested

• Verified on Android with Base App (post-April 2026 update)
• Confirmed window.ethereum injected provider works correctly as fallback
• sdk.isInMiniApp() correctly returns false in Base App WebView, true in Warpcast

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/2	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2