Function execute 

pub fn execute(prepared: PreparedRun, diag_prefix: &str) -> i32

Execute a prepared compatibility run: warnings, --test diagnostics, daemon transition, then the supervised service.

diag_prefix is "" for eggress pproxy run and "pproxy: " for the standalone binary. Logging must already be initialized by the caller: verbosity policy differs per entry point (--log-format vs pretty). Returns the process exit code for --test probes; a serving instance runs until shutdown and exits the process itself on supervisor failure.