add read/write support for .surge.json

[samtalki]

Summary

• Added Surge JSON read/write support at the Network hub with alias handling, JSON sniffing, same format echo, and cross format source warnings.
• Wired Surge through the CLI, Rust reexports, Python surface, C ABI docs, and the format fidelity docs.
• Added Surge fixtures, round trip and conversion tests, and an optional benchmark oracle script.

Testing

• cargo check --workspace
• cargo clippy --all-targets
• cargo test
• cargo fmt --all --check
• rust-analyzer diagnostics .
• bash -n benchmarks/run_validation.sh
• Python syntax checks for the updated test and helper files passed
• The optional local Surge oracle was not fully runnable here because Cargo needed to fetch missing dependencies and the networked build was blocked