Restrict agent roles to bounded configuration overrides (#39299)

## Why

Agent roles should customize a child agent without expanding the authority or changing the provider configuration inherited from its parent session.

## What changed

- Apply only supported role overrides for model behavior, developer instructions, personality, service tier, and capability reductions.
- Preserve parent-owned permissions, model providers, endpoints, MCP servers, notifications, and other unrestricted configuration.
- Keep managed feature requirements effective when a role disables capabilities, and reject symlinked user role files.
- Use the same bounded role application path for both multi-agent implementations and resumed agents.

## Testing

Add coverage for authority preservation, managed feature requirements, symlink rejection, provider inheritance, and provider routing after resume.

GitOrigin-RevId: c528d615b691f9c02bfbc21154d514ea07743010

codex-rs/core/src/agent/control/spawn.rs

@@ -1,6 +1,6 @@
 use super::residency::is_v2_resident_session_source;
 use super::*;
-use crate::agent::role::apply_role_to_config_for_multi_agent_v2;
+use crate::agent::role::apply_role_to_config;
 use crate::config::PermissionProfileSnapshot;
 use crate::context::ContextualUserFragment;
 use crate::context::CurrentTimeReminder;
@@ -310,7 +310,7 @@ impl AgentControl {
                 ),
             };
 
-            apply_role_to_config_for_multi_agent_v2(&mut config, Some(&role_name))
+            apply_role_to_config(&mut config, Some(&role_name))
                 .await
                 .map_err(CodexErr::InvalidRequest)?;
             config