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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[//]: # (BEGIN SAPLING FOOTER)
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* #2424
* __->__ #2423

codex-rs/core/src/config.rs

@@ -3,7 +3,6 @@ use crate::config_types::History;
 use crate::config_types::McpServerConfig;
 use crate::config_types::ReasoningEffort;
 use crate::config_types::ReasoningSummary;
-use crate::config_types::SandboxMode;
 use crate::config_types::SandboxWorkspaceWrite;
 use crate::config_types::ShellEnvironmentPolicy;
 use crate::config_types::ShellEnvironmentPolicyToml;
@@ -16,6 +15,7 @@ use crate::model_provider_info::built_in_model_providers;
 use crate::openai_model_info::get_model_info;
 use crate::protocol::AskForApproval;
 use crate::protocol::SandboxPolicy;
+use codex_protocol::config_types::SandboxMode;
 use dirs::home_dir;
 use serde::Deserialize;
 use std::collections::HashMap;