## Why
The visibility cleanup in the base PR reduced what `codex-mcp` exposes,
but several files still made reviewers read private support machinery
before the public or crate-facing entry points. This ordering pass makes
each file easier to scan: exported API first, crate-visible MCP
internals next, then private helpers in breadth-first order from the
higher-level MCP flows to leaf utilities.
## What Changed
- Reordered `codex-mcp` exports so the runtime, configuration, snapshot,
auth, and helper surfaces are grouped by visibility and reader
importance.
- Moved public and crate-visible MCP items ahead of private helpers in
the auth, MCP planning/snapshot, connection manager, and tool-name
modules.
- Kept the change mechanical, with no behavior changes intended.
## Verification
- `cargo check -p codex-mcp`
Addresses #16971
Problem: Disabled MCP servers were still queried for streamable HTTP
auth status during MCP inventory, so unreachable disabled entries could
add startup latency.
Solution: Return `Unsupported` immediately for disabled MCP server
configs before bearer token/OAuth status discovery.
- Split MCP runtime/server code out of `codex-core` into the new
`codex-mcp` crate. New/moved public structs/types include `McpConfig`,
`McpConnectionManager`, `ToolInfo`, `ToolPluginProvenance`,
`CodexAppsToolsCacheKey`, and the `McpManager` API
(`codex_mcp::mcp::McpManager` plus the `codex_core::mcp::McpManager`
wrapper/shim). New/moved functions include `with_codex_apps_mcp`,
`configured_mcp_servers`, `effective_mcp_servers`,
`collect_mcp_snapshot`, `collect_mcp_snapshot_from_manager`,
`qualified_mcp_tool_name_prefix`, and the MCP auth/skill-dependency
helpers. Why: this creates a focused MCP crate boundary and shrinks
`codex-core` without forcing every consumer to migrate in the same PR.
- Move MCP server config schema and persistence into `codex-config`.
New/moved structs/enums include `AppToolApproval`,
`McpServerToolConfig`, `McpServerConfig`, `RawMcpServerConfig`,
`McpServerTransportConfig`, `McpServerDisabledReason`, and
`codex_config::ConfigEditsBuilder`. New/moved functions include
`load_global_mcp_servers` and
`ConfigEditsBuilder::replace_mcp_servers`/`apply`. Why: MCP TOML
parsing/editing is config ownership, and this keeps config
validation/round-tripping (including per-tool approval overrides and
inline bearer-token rejection) in the config crate instead of
`codex-core`.
- Rewire `codex-core`, app-server, and plugin call sites onto the new
crates. Updated `Config::to_mcp_config(&self, plugins_manager)`,
`codex-rs/core/src/mcp.rs`, `codex-rs/core/src/connectors.rs`,
`codex-rs/core/src/codex.rs`,
`CodexMessageProcessor::list_mcp_server_status_task`, and
`utils/plugins/src/mcp_connector.rs` to build/pass the new MCP
config/runtime types. Why: plugin-provided MCP servers still merge with
user-configured servers, and runtime auth (`CodexAuth`) is threaded into
`with_codex_apps_mcp` / `collect_mcp_snapshot` explicitly so `McpConfig`
stays config-only.
