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/protocol-ts/Cargo.toml

@@ -16,7 +16,6 @@ path = "src/main.rs"
 
 [dependencies]
 anyhow = { workspace = true }
-mcp-types = { workspace = true }
+clap = { workspace = true, features = ["derive"] }
 codex-protocol = { workspace = true }
 ts-rs = { workspace = true }
-clap = { workspace = true, features = ["derive"] }