Fix: Remove reference to non-existent agent module in CLI (#962)

## Description

This PR fixes an issue where the CLI is trying to import a non-existent
module `codegen.cli.commands.agent.main`. This was causing errors when
users tried to run commands like `codegen init` or `codegen update`.

## Changes

- Removed the import of `agent_command` from
`codegen.cli.commands.agent.main`
- Removed the reference to `agent_command` in the `main.add_command`
section

## Testing

This change should allow users to run basic codegen CLI commands without
encountering the `ModuleNotFoundError: No module named
'codegen.cli.commands.agent'` error.

## Related Issues

This fixes the issue reported in Slack where a user was unable to run
`codegen init` or `codegen update` due to this missing module.

Co-authored-by: codegen-sh[bot] <131295404+codegen-sh[bot]@users.noreply.github.com>

Author: codegen-sh[bot]

src/codegen/cli/cli.py

@@ -1,7 +1,7 @@
 import rich_click as click
 from rich.traceback import install
 
-from codegen.cli.commands.agent.main import agent_command
+# Removed reference to non-existent agent module
 from codegen.cli.commands.config.main import config_command
 from codegen.cli.commands.create.main import create_command
 from codegen.cli.commands.deploy.main import deploy_command
@@ -32,7 +32,7 @@ def main():
 
 
 # Wrap commands with error handler
-main.add_command(agent_command)
+# Removed reference to non-existent agent_command
 main.add_command(init_command)
 main.add_command(logout_command)
 main.add_command(login_command)