feat: introduce --profile for Rust CLI (#921)

This introduces a much-needed "profile" concept where users can specify
a collection of options under one name and then pass that via
`--profile` to the CLI.

This PR introduces the `ConfigProfile` struct and makes it a field of
`CargoToml`. It further updates
`Config::load_from_base_config_with_overrides()` to respect
`ConfigProfile`, overriding default values where appropriate. A detailed
unit test is added at the end of `config.rs` to verify this behavior.

Details on how to use this feature have also been added to
`codex-rs/README.md`.

codex-rs/mcp-server/src/codex_tool_config.rs

@@ -22,6 +22,10 @@ pub(crate) struct CodexToolCallParam {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub model: Option<String>,
 
+    /// Configuration profile from config.toml to specify default options.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub profile: Option<String>,
+
     /// Working directory for the session. If relative, it is resolved against
     /// the server process's current working directory.
     #[serde(default, skip_serializing_if = "Option::is_none")]
@@ -144,6 +148,7 @@ impl CodexToolCallParam {
         let Self {
             prompt,
             model,
+            profile,
             cwd,
             approval_policy,
             sandbox_permissions,
@@ -156,11 +161,12 @@ impl CodexToolCallParam {
         // Build ConfigOverrides recognised by codex-core.
         let overrides = codex_core::config::ConfigOverrides {
             model,
+            config_profile: profile,
             cwd: cwd.map(PathBuf::from),
             approval_policy: approval_policy.map(Into::into),
             sandbox_policy,
             disable_response_storage,
-            provider: None,
+            model_provider: None,
         };
 
         let cfg = codex_core::config::Config::load_with_overrides(overrides)?;
@@ -218,6 +224,10 @@ mod tests {
                 "description": "Optional override for the model name (e.g. \"o3\", \"o4-mini\")",
                 "type": "string"
               },
+              "profile": {
+                "description": "Configuration profile from config.toml to specify default options.",
+                "type": "string"
+              },
               "prompt": {
                 "description": "The *initial user prompt* to start the Codex conversation.",
                 "type": "string"