cli: fix zsh completion

[tamird]

Before this change:

tamird@L03G26TD12 codex-rs % codex
zsh: do you wish to see all 3864 possibilities (1285 lines)?

After this change:

tamird@L03G26TD12 codex-rs % codex
app-server              -- [experimental] Run the app server
apply                a  -- Apply the latest diff produced by Codex agent as a `git apply` to your local working tree
cloud                   -- [EXPERIMENTAL] Browse tasks from Codex Cloud and apply changes locally
completion              -- Generate shell completion scripts
debug                   -- Internal debugging commands
exec                 e  -- Run Codex non-interactively
generate-ts             -- Internal: generate TypeScript protocol bindings
help                    -- Print this message or the help of the given subcommand(s)
login                   -- Manage login
logout                  -- Remove stored authentication credentials
mcp                     -- [experimental] Run Codex as an MCP server and manage MCP servers
mcp-server              -- [experimental] Run the Codex MCP server (stdio transport)
responses-api-proxy     -- Internal: run the responses API proxy
resume                  -- Resume a previous interactive session (picker by default; use --last to continue the most recent)

[github-actions]

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[tamird]

I have read the CLA Document and I hereby sign the CLA