feat: make reasoning effort/summaries configurable (#1199)

Previous to this PR, we always set `reasoning` when making a request
using the Responses API:


d7245cbbc9/codex-rs/core/src/client.rs (L108-L111)

Though if you tried to use the Rust CLI with `--model gpt-4.1`, this
would fail with:

```shell
"Unsupported parameter: 'reasoning.effort' is not supported with this model."
```

We take a cue from the TypeScript CLI, which does a check on the model
name:


d7245cbbc9/codex-cli/src/utils/agent/agent-loop.ts (L786-L789)

This PR does a similar check, though also adds support for the following
config options:

```
model_reasoning_effort = "low" | "medium" | "high" | "none"
model_reasoning_summary = "auto" | "concise" | "detailed" | "none"
```

This way, if you have a model whose name happens to start with `"o"` (or
`"codex"`?), you can set these to `"none"` to explicitly disable
reasoning, if necessary. (That said, it seems unlikely anyone would use
the Responses API with non-OpenAI models, but we provide an escape
hatch, anyway.)

This PR also updates both the TUI and `codex exec` to show `reasoning
effort` and `reasoning summaries` in the header.

codex-rs/exec/src/event_processor.rs

@@ -1,5 +1,7 @@
 use codex_common::elapsed::format_elapsed;
+use codex_core::WireApi;
 use codex_core::config::Config;
+use codex_core::model_supports_reasoning_summaries;
 use codex_core::protocol::AgentMessageEvent;
 use codex_core::protocol::BackgroundEventEvent;
 use codex_core::protocol::ErrorEvent;
@@ -127,16 +129,28 @@ impl EventProcessor {
             VERSION
         );
 
-        let entries = vec![
+        let mut entries = vec![
             ("workdir", config.cwd.display().to_string()),
             ("model", config.model.clone()),
             ("provider", config.model_provider_id.clone()),
             ("approval", format!("{:?}", config.approval_policy)),
             ("sandbox", format!("{:?}", config.sandbox_policy)),
         ];
+        if config.model_provider.wire_api == WireApi::Responses
+            && model_supports_reasoning_summaries(&config.model)
+        {
+            entries.push((
+                "reasoning effort",
+                config.model_reasoning_effort.to_string(),
+            ));
+            entries.push((
+                "reasoning summaries",
+                config.model_reasoning_summary.to_string(),
+            ));
+        }
 
         for (key, value) in entries {
-            println!("{} {}", format!("{key}: ").style(self.bold), value);
+            println!("{} {}", format!("{key}:").style(self.bold), value);
         }
 
         println!("--------");