chore: move mcp-server/src/wire_format.rs to protocol/src/mcp_protocol.rs (#2423)

The existing `wire_format.rs` should share more types with the
`codex-protocol` crate (like `AskForApproval` instead of maintaining a
parallel `CodexToolCallApprovalPolicy` enum), so this PR moves
`wire_format.rs` into `codex-protocol`, renaming it as
`mcp-protocol.rs`. We also de-dupe types, where appropriate.

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* #2424
* __->__ #2423

codex-rs/mcp-server/src/lib.rs

@@ -24,7 +24,6 @@ mod json_to_toml;
 pub(crate) mod message_processor;
 mod outgoing_message;
 mod patch_approval;
-pub mod wire_format;
 
 use crate::message_processor::MessageProcessor;
 use crate::outgoing_message::OutgoingMessage;