Support enable/disable skill via config/api. (#9328)

In config.toml:
```
[[skills.config]]
path = "/Users/xl/.codex/skills/my_skill/SKILL.md"
enabled = false
```

API:
skills/list, skills/config/write

codex-rs/tui/src/chatwidget.rs

@@ -622,7 +622,7 @@ impl ChatWidget {
         self.submit_op(Op::ListCustomPrompts);
         self.submit_op(Op::ListSkills {
             cwds: Vec::new(),
-            force_reload: false,
+            force_reload: true,
         });
         if let Some(user_message) = self.initial_user_message.take() {
             self.submit_user_message(user_message);