feat: Support listing and selecting skills via $ or /skills (#7506)

List/Select skills with $-mention or /skills

codex-rs/tui/src/slash_command.rs

@@ -14,6 +14,7 @@ pub enum SlashCommand {
     // more frequently used commands should be listed first.
     Model,
     Approvals,
+    Skills,
     Review,
     New,
     Resume,
@@ -46,6 +47,7 @@ impl SlashCommand {
             SlashCommand::Quit | SlashCommand::Exit => "exit Codex",
             SlashCommand::Diff => "show git diff (including untracked files)",
             SlashCommand::Mention => "mention a file",
+            SlashCommand::Skills => "use skills to improve how Codex performs specific tasks",
             SlashCommand::Status => "show current session configuration and token usage",
             SlashCommand::Model => "choose what model and reasoning effort to use",
             SlashCommand::Approvals => "choose what Codex can do without approval",
@@ -76,6 +78,7 @@ impl SlashCommand {
             | SlashCommand::Logout => false,
             SlashCommand::Diff
             | SlashCommand::Mention
+            | SlashCommand::Skills
             | SlashCommand::Status
             | SlashCommand::Mcp
             | SlashCommand::Feedback