feat(settings): add Skills toggle for Codex CLI and improve config editor UX

Add "Enable Skills" toggle below "Enable WebSocket" in Codex CLI settings,
writing `skills = true` under [features] in config.toml. Also add max-height
to auth.json and config.toml textareas, and fix TOML section key insertion
to avoid stray blank lines between entries.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/i18n/messages/en.json

@@ -515,6 +515,8 @@
       "selectReasoningEffort": "Select Reasoning Effort",
       "enableWebsocket": "Enable WebSocket",
       "enableWebsocketAria": "Enable WebSocket for Codex Provider",
+      "enableSkills": "Enable Skills",
+      "enableSkillsAria": "Enable Skills for Codex",
       "authJsonNative": "auth.json (native)",
       "configTomlNative": "config.toml (native)"
     },