[v1] Replace demo-node examples with toolkit examples

[SMC17]

Problem
The v1 release needs this work to make the toolkit claim defensible.

Scope

• Replace or demote demo-node examples so the examples sell the actual v1 product.
• Keep unsupported demos clearly marked experimental.

Files

• examples/simple_payment.zig
• examples/http_server_demo.zig
• examples/network_demo.zig
• examples/ledger_consensus.zig
• README.md

Gates

• Gate A

Acceptance Criteria

• Examples focus on codec, signing, and conformance workflows.
• Experimental node demos are moved or clearly labeled non-v1.
• README points only to supported examples in the v1 section.

Related

• Epic: [Epic] v1 XRPL Toolkit release #45
• Milestone: v1 XRPL Toolkit