fix: clean up TypeScript exports (#4518)

Fixes:

- Removed overdeclaration of types that were unnecessary because they
were already included by induction.
- Reordered list of response types to match the enum order, making it
easier to identify what was missing.
- Added `ExecArbitraryCommandResponse` because it was missing.
- Leveraged `use codex_protocol::mcp_protocol::*;` to make the file more
readable.
- Removed crate dependency on `mcp-types` now that we have separate the
app server from the MCP server:
https://github.com/openai/codex/pull/4471

My next move is to come up with some scheme that ensures request types
always have a response type and that the response type is automatically
included with the output of `codex generate-ts`.

codex-rs/Cargo.lock

@@ -1125,7 +1125,6 @@ dependencies = [
  "anyhow",
  "clap",
  "codex-protocol",
- "mcp-types",
  "ts-rs",
 ]