FFX `zxdb` Integration (`ffx_zxdb`)

This crate contains the host Rust library that integrates zxdb with ffx subtools (ffx debug, ffx component, and ffx test).

Interface

The crate root (src/README.md) re-exports these entry points:

CommandBuilder: Builder for zxdb command-line arguments.
Debugger and debugger::DebuggerSession: High-level controller that spawns zxdb and manages the background socket-forwarding task.
debug_agent::{DebugAgentSocket, DebuggerProxy}: Local UNIX domain socket listener and FDomain FIDL proxy wrapper.
spawn_forward_task and forward_to_agent: Asynchronous and blocking connection forwarders between UNIX domain sockets and FDomain FIDL sockets.
util::{Agent, get_all_debug_agents, print_debug_agents}: Helpers that query and print active target DebugAgent instances.

Callers and implementations must preserve these invariants:

DebugAgentSocket::forward_one_connection accepts local UNIX socket connections before opening remote FDomain FIDL socket connections.
DebuggerSession keeps background socket-forwarding tasks alive for its entire lifetime, and Debugger::start blocks until zxdb sends SIGUSR1.
Code in this crate follows //src/developer/ffx/AGENTS.md (Rust edition 2024, *_rust_fdomain bindings, fho::Result/thiserror in new or refactored code, and #[fuchsia::test]).

Using ffx_zxdb produces these host and target side effects:

Creates and deletes temporary UNIX domain socket files in std::env::temp_dir().
Registers the symbol index, spawns the local zxdb host binary, and calls fuchsia.debugger FIDL methods over FDomain.

Run this command to build ffx_zxdb: