Adds localnet testing mode to gateway-probe for LP development:
- Add TestMode enum for different probe configurations
- Add --gateway-ip flag for direct gateway testing
- Implement two-hop WireGuard tunnel for localnet
- Add mock ecash support for testing without real credentials
- Add netstack Go bindings for userspace networking
- Restructure probe with mode and common modules
- Update README with localnet mode documentation
Extends LP protocol with telescoping architecture for nested sessions:
- Add nested session support with KKpsk0 rekeying
- Add subsession support with collision detection
- Implement unified packet format with outer header
- Refactor gateway handlers for single-packet forwarding
- Add TTL-based state cleanup for stale sessions
- Add outer AEAD encryption layer
- Refactor registration client for packet-per-connection model