Fix flaky windows CI test (#10993)

Hardens PTY Python REPL test and make MCP test startup deterministic

**Summary**
- `utils/pty/src/tests.rs`
- Added a REPL readiness handshake (`wait_for_python_repl_ready`) that
repeatedly sends a marker and waits for it in PTY output before sending
test commands.
  - Updated `pty_python_repl_emits_output_and_exits` to:
    - wait for readiness first,
    - preserve startup output,
    - append output collected through process exit.
- Reduces Windows/ConPTY flakiness from early stdin writes racing REPL
startup.

- `mcp-server/tests/suite/codex_tool.rs`
- Avoid remote model refresh during MCP test startup, reducing
timeout-prone nondeterminism.

codex-rs/mcp-server/tests/suite/codex_tool.rs

@@ -505,6 +505,9 @@ base_url = "{server_uri}/v1"
 wire_api = "responses"
 request_max_retries = 0
 stream_max_retries = 0
+
+[features]
+remote_models = false
 "#
         ),
     )