Solana clients cannot pay for any GET endpoint (402 rejected before signing)

[VickyXAI]

Problem

doGetWithPayment rejects every 402 on a GET when bc.privateKey == nil:

https://github.com/BlockRunAI/blockrun-llm-go/blob/main/base_client.go#L358-L361

if resp.StatusCode == http.StatusPaymentRequired {
    if bc.privateKey == nil {
        return nil, &PaymentError{Message: "endpoint returned 402 but no wallet is configured"}
    }
    return bc.handleGetPaymentAndRetry(ctx, url, resp)
}

But privateKey is nil for Solana by design — the baseClient doc comment says so directly:

// The default chain is Base (EIP-712 signing with privateKey). When chain is
// "solana" the client pays USDC on Solana instead: privateKey is nil, solanaKey
// holds the bs58 signing key, and address is the bs58 public key.

So Solana clients never reach createPaymentPayload on a GET. They get a misleading "no wallet is configured" error even with a perfectly good Solana key loaded.

Impact

Every paid GET surface fails for Solana users:

• dex.go:28 — /v1/zerox/
• market.go:113,150,186 — market data
• prediction_market.go:22 — prediction markets
• defi.go:26 — /v1/defillama/
• surf.go:244 — /v1/surf/

POST paths are unaffected (they use a different code path), which is why this has gone unnoticed.

Fix

Make the guard check that any signing key is configured, rather than the Base one specifically:

if bc.privateKey == nil && bc.solanaKey == "" {
    return nil, &PaymentError{Message: "endpoint returned 402 but no wallet is configured"}
}

base_client.go:359 is the only privateKey == nil guard in the repo, so this is a one-condition change. Worth a regression test that drives a Solana client through a paid GET.

Provenance

Surfaced by Codex during the /review pass on #7 while tracing callers of CreateSolanaPaymentPayload. Not introduced by #7 — kept out of that PR to avoid widening the blast radius of a payment-path change.