feat: shell command explanation option (#173)

# Shell Command Explanation Option

## Description
This PR adds an option to explain shell commands when the user is
prompted to approve them (Fixes #110). When reviewing a shell command,
users can now select "Explain this command" to get a detailed
explanation of what the command does before deciding whether to approve
or reject it.

## Changes
- Added a new "EXPLAIN" option to the `ReviewDecision` enum
- Updated the command review UI to include an "Explain this command (x)"
option
- Implemented the logic to send the command to the LLM for explanation
using the same model as the agent
- Added a display for the explanation in the command review UI
- Updated all relevant components to pass the explanation through the
component tree

## Benefits
- Improves user understanding of shell commands before approving them
- Reduces the risk of approving potentially harmful commands
- Enhances the educational aspect of the tool, helping users learn about
shell commands
- Maintains the same workflow with minimal UI changes

## Testing
- Manually tested the explanation feature with various shell commands
- Verified that the explanation is displayed correctly in the UI
- Confirmed that the user can still approve or reject the command after
viewing the explanation

## Screenshots

![improved_shell_explanation_demo](https://github.com/user-attachments/assets/05923481-29db-4eba-9cc6-5e92301d2be0)


## Additional Notes
The explanation is generated using the same model as the agent, ensuring
consistency in the quality and style of explanations.

---------

Signed-off-by: crazywolf132 <crazywolf132@gmail.com>

codex-cli/package.json

@@ -37,8 +37,10 @@
     "diff": "^7.0.0",
     "dotenv": "^16.1.4",
     "fast-deep-equal": "^3.1.3",
+    "figures": "^6.1.0",
     "file-type": "^20.1.0",
     "ink": "^5.2.0",
+    "js-yaml": "^4.1.0",
     "marked": "^15.0.7",
     "marked-terminal": "^7.3.0",
     "meow": "^13.2.0",
@@ -46,8 +48,10 @@
     "openai": "^4.89.0",
     "react": "^18.2.0",
     "shell-quote": "^1.8.2",
+    "strip-ansi": "^7.1.0",
     "to-rotated": "^1.0.0",
-    "use-interval": "1.4.0"
+    "use-interval": "1.4.0",
+    "zod": "^3.24.3"
   },
   "devDependencies": {
     "@eslint/js": "^9.22.0",