docs: Stellar React hooks reference (#68)

- Add reference/stellar-react-hooks.mdx with full hook reference
- Cover useStellarStealthKeys, useStellarAnnouncementScan,
  useStellarSendStealthPayment, useStellarName, useStellarBalance
- Include signatures, params, return types, JSX examples, pitfalls
- Add React Strict Mode and React Native caveat sections
- Add full app example using all five hooks
- Link from SDK Stellar page and getting-started

Gated on @wraith-protocol/sdk-react shipping.

Author: boalambo

.gitignore

@@ -1,3 +1,2 @@
-reference/
 node_modules/
-.npm/
+.npm/

getting-started.mdx

@@ -149,5 +149,6 @@ try {
 - [Single-Chain Agent Guide](guides/single-chain-agent) — deeper walkthrough
 - [Multichain Agent Guide](guides/multichain-agent) — deploy across multiple chains
 - [Bring Your Own Model](guides/bring-your-own-model) — use OpenAI or Claude instead of Gemini
+- [Stellar React Hooks](sdk/stellar-react-hooks) — React hooks for Stellar stealth address operations
 - [Stellar Troubleshooting](guides/stellar-troubleshooting) — fixes for common Stellar, Soroban, and Stealth errors
 - [SDK Reference](sdk/agent-client) — full API documentation