Fix compile errors: add libp2p dep, re-export PeerSnapshot, remove unused miner variable

[dill-lk]

Motivation

• Resolve unresolved crate and type errors preventing the lattice binary from compiling by making required symbols available to bins/lattice at build time.
• Make PeerSnapshot available from the lattice-rpc crate root so downstream consumers can import it as lattice_rpc::PeerSnapshot.
• Remove an unused local binding in the miner that triggered -D warnings and failed the build.

Description

• Add the workspace libp2p dependency to the lattice binary by updating bins/lattice/Cargo.toml so use libp2p::... imports resolve.
• Re-export PeerSnapshot from crates/lattice-rpc/src/lib.rs by changing pub use handlers::{ChainState, RpcHandlers}; to pub use handlers::{ChainState, PeerSnapshot, RpcHandlers}; so PeerSnapshot is available at the crate root.
• Remove the unused current_height binding in bins/lattice/src/miner/mod.rs to eliminate the unused variable compile error under -D warnings.

Testing

• Ran cargo check -p lattice which progressed past the originally reported Rust symbol and unused-variable errors but continued into long-running native dependency compilation (RocksDB and other crates) and was stopped by the environment before completing.
• Ran cargo check -p lattice-rpc which also compiled past the earlier export error and reached heavy native compilation and was stopped for the same environment limitation.

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Codex Task

[gemini-code-assist]

Code Review

This pull request adds the libp2p dependency to the lattice binary, removes an unused current_height variable from the miner implementation, and exports PeerSnapshot from the lattice-rpc crate. I have no feedback to provide as there are no review comments or issues identified.

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