chore(antithesis): Generate configs for scenario purposes

ADP and Datadog Agent support an intersection of datadog.yaml config
options but ADP has distinct configuration from Datadog Agent and vice
versa. Some of that is temporary, some is a permanent state.

Author: blt

test/antithesis/harness/src/bin/first_sample_config/main.rs

@@ -1,22 +1,20 @@
 //! Antithesis `first_` command: sample this timeline's `datadog.yaml` and release ADP.
 //!
 //! Runs once per execution path after `setup_complete`, so the sample (see
-//! [`config`], Antithesis SDK randomness) is a post-snapshot, per-timeline
+//! [`harness::config`], Antithesis SDK randomness) is a post-snapshot, per-timeline
 //! decision Antithesis branches. Writes the config to the shared `agent-config`
 //! volume then a `ready` sentinel the blocked ADP entrypoint waits on; running
 //! upstream of ADP's boot is what makes each timeline boot under its own config.
 //! Deployment fields come from the environment (see [`Cli`]).
 
-mod config;
-
 use std::fs;
 use std::path::PathBuf;
 
 use antithesis_sdk::prelude::*;
 use antithesis_sdk::random::AntithesisRng;
 use anyhow::Context as _;
 use clap::Parser;
-use config::DatadogConfig;
+use harness::config::{ConfigProfile, DatadogConfig};
 use rand::rand_core::UnwrapErr;
 use serde_json::json;
 
@@ -28,6 +26,11 @@ struct Cli {
     /// `agent-config` volume; the ADP container reads it).
     #[arg(long, env = "CONFIG_DIR", default_value = "/agent-config")]
     config_dir: PathBuf,
+    /// Which `datadog.yaml` variation to sample. The differential scenario sets
+    /// `CONFIG_PROFILE=differential` so both targets share a config they can both
+    /// honor; ADP-only scenarios keep the default full feral surface.
+    #[arg(long, env = "CONFIG_PROFILE", value_enum, default_value_t = ConfigProfile::General)]
+    profile: ConfigProfile,
     /// Agent hostname written into the config. (`DD_HOSTNAME`, not the ambient
     /// `HOSTNAME`, so a container's own hostname does not leak in.)
     #[arg(long, env = "DD_HOSTNAME", default_value = "antithesis-adp")]
@@ -57,6 +60,7 @@ fn main() -> anyhow::Result<()> {
         &cli.api_key,
         &cli.dd_url,
         &cli.dogstatsd_socket,
+        cli.profile,
     );
 
     let yaml_path = cli.config_dir.join("datadog.yaml");