Improve Solana swap stability and demo RPC guidance

[veithly]

Summary

• add early validation/logging to SolanaSwapTool and map native SOL to the wrapped SOL mint when calling Jupiter
• make decimal resolution and Jupiter quote fetching more robust (fallback decimals for wSOL, timeouts, detailed DNS/HTTP error messages)
• update solana_toolkit_demo to enforce rpc_url/private key guidance, include wallet info tool for swaps, and gate scenarios based on presence of environment private key

Testing

• Not run (not requested)