fn resolve_srv_binary(launcher_exe_dir: &Path) -> Result<PathBuf, SrvSpawnError>Expand description
Resolve the agentmux-srv binary path from the LAUNCHER’s vantage point.
Search order, mirroring the host’s resolve_backend_binary in
sidecar.rs (minus its workspace dist/bin fallback) but anchored at
the launcher’s exe dir:
<launcher_dir>/runtime/agentmux-srv-{ver}-{os}.{arch}.exe(versioned portable layout)<launcher_dir>/runtime/agentmux-srv.exe(dev fallback)<launcher_dir>/agentmux-srv-{ver}-{os}.{arch}.exe(launcher in same dir as srv — should not happen in portable but covers cargo-built dev mode where launcher + srv both land in target/release/)<launcher_dir>/agentmux-srv.exe(dev fallback)