feat: Add more /review options (#3961)

Adds the following options:

1. Review current changes
2. Review a specific commit
3. Review against a base branch (PR style)
4. Custom instructions

<img width="487" height="330" alt="Screenshot 2025-09-20 at 2 11 36 PM"
src="https://github.com/user-attachments/assets/edb0aaa5-5747-47fa-881f-cc4c4f7fe8bc"
/>

---

\+ Adds the following UI helpers:

1. Makes list selection searchable
2. Adds navigation to the bottom pane, so you could add a stack of
popups
3. Basic custom prompt view

codex-rs/tui/src/app.rs

@@ -354,6 +354,18 @@ impl App {
             AppEvent::UpdateSandboxPolicy(policy) => {
                 self.chat_widget.set_sandbox_policy(policy);
             }
+            AppEvent::OpenReviewBranchPicker(cwd) => {
+                self.chat_widget.show_review_branch_picker(&cwd).await;
+            }
+            AppEvent::OpenReviewCommitPicker(cwd) => {
+                self.chat_widget.show_review_commit_picker(&cwd).await;
+            }
+            AppEvent::OpenReviewCustomPrompt => {
+                self.chat_widget.show_review_custom_prompt();
+            }
+            AppEvent::OpenReviewPopup => {
+                self.chat_widget.open_review_popup();
+            }
         }
         Ok(true)
     }