feat: /review (#3774)

Adds `/review` action in TUI

<img width="637" height="370" alt="Screenshot 2025-09-17 at 12 41 19 AM"
src="https://github.com/user-attachments/assets/b1979a6e-844a-4b97-ab20-107c185aec1d"
/>

codex-rs/tui/src/slash_command.rs

@@ -14,6 +14,7 @@ pub enum SlashCommand {
     // more frequently used commands should be listed first.
     Model,
     Approvals,
+    Review,
     New,
     Init,
     Compact,
@@ -34,6 +35,7 @@ impl SlashCommand {
             SlashCommand::New => "start a new chat during a conversation",
             SlashCommand::Init => "create an AGENTS.md file with instructions for Codex",
             SlashCommand::Compact => "summarize conversation to prevent hitting the context limit",
+            SlashCommand::Review => "review my current changes and find issues",
             SlashCommand::Quit => "exit Codex",
             SlashCommand::Diff => "show git diff (including untracked files)",
             SlashCommand::Mention => "mention a file",
@@ -61,6 +63,7 @@ impl SlashCommand {
             | SlashCommand::Compact
             | SlashCommand::Model
             | SlashCommand::Approvals
+            | SlashCommand::Review
             | SlashCommand::Logout => false,
             SlashCommand::Diff
             | SlashCommand::Mention