[codex-app-server-test-client & codex-app-server] Plugin Usage Analytics Smoke Test (#27099)

## This PR

The original [combined remote plugin analytics PR
#26281](https://github.com/openai/codex/pull/26281) mixed reusable
analytics test infrastructure, two manual smoke workflows, a metadata
refactor, and the final identity behavior. This PR establishes a
non-mutating end-to-end plugin smoke workflow before any analytics
identity semantics change.

- Add `plugin-analytics-smoke` to the existing app-server test client.
- Exercise plugin disable, enable, and use through production app-server
RPC paths.
- Isolate config writes in a temporary file and use a loopback Responses
API server.
- Capture analytics without sending them to the production analytics
backend.
- Validate the current local `plugin_id`, names, capability metadata,
thread, turn, and model fields.

This is intentionally a baseline smoke workflow. It does not assert
`remote_plugin_id`; the final PR will update it when that field exists.
Review this PR as the net diff against #27093.

## Testing

- The test-client target compiles successfully.
- The combined reference branch exercised the manual smoke against the
live remote plugin service.
- CI is green across the required platform matrix.

## Split Overview

```text
main
├── #27093  Debug analytics capture
│   └── #27099  Non-mutating plugin smoke           ← you are here
│       └── #27100  Remote install/uninstall smoke
└── #27102  Plugin telemetry metadata refactor

After #27093, #27099, #27100, and #27102 merge:
└── Final PR: add remote_plugin_id to plugin analytics
```

Review order and dependencies:

1. [#27093 Add debug-only analytics event
capture](https://github.com/openai/codex/pull/27093) (based on `main`)
2. [#27099 Add a plugin analytics smoke
workflow](https://github.com/openai/codex/pull/27099) **(this PR,
stacked on #27093)**
3. [#27100 Add a remote plugin analytics mutation smoke
workflow](https://github.com/openai/codex/pull/27100) (stacked on this
PR)
4. [#27102 Centralize plugin telemetry metadata
construction](https://github.com/openai/codex/pull/27102) (independent,
based on `main`)
5. Final remote-ID behavior PR (created after PRs 1-4 merge)

The original [#26281](https://github.com/openai/codex/pull/26281)
remains open as the green aggregate reference until the final PR is
published.

codex-rs/app-server-test-client/src/lib.rs

@@ -87,6 +87,9 @@ use tungstenite::stream::MaybeTlsStream;
 use url::Url;
 use uuid::Uuid;
 
+mod loopback_responses_server;
+mod plugin_analytics_smoke;
+
 const NOTIFICATIONS_TO_OPT_OUT: &[&str] = &[
     // v2 item deltas.
     "command/exec/outputDelta",
@@ -272,6 +275,16 @@ enum CliCommand {
         #[arg(long, default_value_t = 15)]
         hold_seconds: u64,
     },
+    /// Exercise remote plugin analytics through production app-server RPC paths.
+    #[command(name = "plugin-analytics-smoke")]
+    PluginAnalyticsSmoke {
+        /// Installed local plugin id, such as `linear@openai-curated-remote`.
+        #[arg(long)]
+        plugin_id: String,
+        /// JSONL output path. Defaults to a PID-specific file under the system temp directory.
+        #[arg(long)]
+        capture_file: Option<PathBuf>,
+    },
 }
 
 pub async fn run() -> Result<()> {
@@ -423,6 +436,17 @@ pub async fn run() -> Result<()> {
                 hold_seconds,
             )
         }
+        CliCommand::PluginAnalyticsSmoke {
+            plugin_id,
+            capture_file,
+        } => {
+            ensure_dynamic_tools_unused(&dynamic_tools, "plugin-analytics-smoke")?;
+            if url.is_some() {
+                bail!("plugin-analytics-smoke requires --codex-bin and does not support --url");
+            }
+            let codex_bin = codex_bin.context("plugin-analytics-smoke requires --codex-bin")?;
+            plugin_analytics_smoke::run(&codex_bin, &config_overrides, &plugin_id, capture_file)
+        }
     }
 }
 
@@ -1440,6 +1464,14 @@ impl CodexClient {
     }
 
     fn spawn_stdio(codex_bin: &Path, config_overrides: &[String]) -> Result<Self> {
+        Self::spawn_stdio_with_env(codex_bin, config_overrides, &[])
+    }
+
+    fn spawn_stdio_with_env(
+        codex_bin: &Path,
+        config_overrides: &[String],
+        environment: &[(OsString, OsString)],
+    ) -> Result<Self> {
         let codex_bin_display = codex_bin.display();
         let mut cmd = Command::new(codex_bin);
         if let Some(codex_bin_parent) = codex_bin.parent() {
@@ -1453,6 +1485,9 @@ impl CodexClient {
         for override_kv in config_overrides {
             cmd.arg("--config").arg(override_kv);
         }
+        for (name, value) in environment {
+            cmd.env(name, value);
+        }
         let mut codex_app_server = cmd
             .arg("app-server")
             .stdin(Stdio::piped())