feat(codex): accept --yolo launch flag

[RichelynScott]

Summary

Codex CLI ships a hidden --yolo alias for --full-auto (equivalent to --dangerously-bypass-approvals-and-sandbox). hcom's Codex argument allowlist rejects it before launch, so hcom codex --yolo fails even though the underlying codex --yolo --version works:

$ hcom codex --yolo
Error: unrecognized flag: --yolo

This PR adds --yolo to the parser allowlist, sandbox-group set, and the hcom-writable sandbox-active detector — behavior parallels the existing handling for --full-auto and --dangerously-bypass-approvals-and-sandbox.

Changes

• src/tools/codex_args.rs:
  • BOOLEAN_FLAGS adds --yolo (parser accepts it as a no-arg flag)
  • SANDBOX_FLAGS adds --yolo (treated as a sandbox-group override during arg merge)
  • New unit test test_parse_yolo_hidden_alias
  • New unit test test_merge_yolo_overrides_sandbox_group
  • Existing test_parse_boolean_flags extended to cover --yolo
• src/tools/codex_preprocessing.rs:
  • ensure_hcom_writable sandbox-active list adds --yolo (so hcom CWD lands in --add-dir set)
  • New unit test test_ensure_hcom_writable_treats_yolo_as_sandbox_active
  • New unit test test_preprocess_yolo_overrides_hcom_default_sandbox

No dependency changes. No schema or CLI-contract changes for existing flags. Doc updates intentionally omitted — happy to add if you'd prefer them in this PR.

Test plan

• cargo test --release --locked passes locally (all 4 new tests + full suite)
• cargo clippy --all-targets --locked -- -D warnings clean
• cargo fmt --all -- --check clean
• Manual: hcom codex --yolo accepts the flag and propagates it through preprocessing with sandbox-active treatment
• CI: would benefit from confirmation on macOS / Windows runners

Branched from aannoo/hcom@main and squash-friendly — single focused commit.

[aannoo]

thanks!