feat: add Codex Apps sediment file remapping (#15197)

## Summary
- bridge Codex Apps tools that declare `_meta["openai/fileParams"]`
through the OpenAI file upload flow
- mask those file params in model-visible tool schemas so the model
provides absolute local file paths instead of raw file payload objects
- rewrite those local file path arguments client-side into
`ProvidedFilePayload`-shaped objects before the normal MCP tool call

## Details
- applies to scalar and array file params declared in
`openai/fileParams`
- Codex uploads local files directly to the backend and uses the
uploaded file metadata to build the MCP tool arguments locally
- this PR is input-only

## Verification
- `just fmt`
- `cargo test -p codex-core mcp_tool_call -- --nocapture`

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/core/tests/suite/mod.rs

@@ -106,6 +106,7 @@ mod model_switching;
 mod model_visible_layout;
 mod models_cache_ttl;
 mod models_etag_responses;
+mod openai_file_mcp;
 mod otel;
 mod pending_input;
 mod permissions_messages;