fix(codex): pass prompts via stdin

[attid]

Summary

Pass Codex prompts through stdin instead of argv on all platforms.

Why

Ductor composes prompts with hooks, background task context, and memory. Passing the full prompt as a command-line argument can exceed Linux argv limits before the Codex CLI starts, raising OSError: [Errno 7] Argument list too long.

Changes

• Use - as the Codex prompt marker for new and resumed codex exec calls.
• Add optional stdin payload support to the shared CLI subprocess executor.
• Keep Dockerized Codex stdin open with docker exec -i so piped prompts arrive.
• Cover non-streaming, resume, streaming, and CLI parameter command shape with tests.

Validation

• uv run pytest tests/cli/test_codex_provider.py tests/integration/test_cli_parameter_flow.py tests/cli/test_executor_timeout.py tests/cli/test_claude_provider.py tests/cli/test_docker_wrap.py -q
• uv run ruff check ductor_bot/cli/base.py ductor_bot/cli/executor.py ductor_bot/cli/codex_provider.py tests/cli/test_codex_provider.py tests/integration/test_cli_parameter_flow.py
• uv run mypy ductor_bot