fix: retry wallet connect on WalletNotSelectedError to fix first-select race

[SAY-5]

Summary

Closes #2.

`select(walletName)` triggers a React state update; the auto-connect
`useEffect` then sees `wallet` truthy and calls `connect()` from
`useWallet()`. On the first selection after the modal mounts,
the @solana/wallet-adapter-react WalletContext has not always finished
registering the underlying adapter by the time this effect re-runs,
so `connect()` throws `WalletNotSelectedError` and the wallet
popup never opens. Clicking again succeeds because the second pass
sees a fully-registered adapter.

Fix

Wrap the auto-connect in a small async helper that retries once
after 200ms when, and only when, the failure is
`WalletNotSelectedError`. Other errors, user rejection, timeout,
session-expired, propagate to `setError` unchanged.

The effect's cleanup cancels both an in-flight retry timer and any
post-`await` state writes, so a re-mount or wallet switch during
the retry window doesn't leak a state update or a stray retry call.

The original code's behaviour for the happy path (`connect`
resolves on first try) and for non-race errors is preserved
verbatim, the retry only fires for `WalletNotSelectedError` and
only once per selection.

Test plan

• `npm run build` (rollup) succeeds with the change applied.
• Manual smoke test in a real browser with a Solana wallet
  extension installed (would confirm the popup opens on first
  select). I don't have a desktop Solana wallet installed in
  this environment, so I'm relying on review for the runtime
  check.

Notes on alternatives considered

The issue body lists three options. I went with the retry approach
(option 3) because:

• Option 1 (ref instead of state) needs a wider refactor of the
  connecting flag and is more invasive.
• Option 2 (`wallet?.adapter.connect()` directly) bypasses the
  WalletContext layer and risks the context's internal state going
  out of sync with the adapter's connected state for downstream
  hooks (`publicKey`, `sendTransaction`).
• Option 3 is a localised, explicit, single-retry guard against a
  known race; it leaves all other paths untouched and is easy to
  remove later if @solana/wallet-adapter-react fixes the race
  upstream.