## Why
The root Python formatting pass only covered `scripts/`, leaving Python utilities elsewhere in the repository outside `just fmt` and `just fmt-check`.
## What changed
- Run the scripts Ruff formatter from the repository root.
- Exclude `sdk/python`, which has its own formatter pass, and `codex-rs/vendor`.
- Apply Ruff formatting to the newly covered Python files and update the formatter coverage test.
GitOrigin-RevId: 73ac82b8bb9c713d589724f6c4f926399febb513
Problem: The TUI still depended on `codex-core` directly in a number of
places, and we had no enforcement from keeping this problem from getting
worse.
Solution: Route TUI core access through
`codex-app-server-client::legacy_core`, add CI enforcement for that
boundary, and re-export this legacy bridge inside the TUI as
`crate::legacy_core` so the remaining call sites stay readable. There is
no functional change in this PR — just changes to import targets.
Over time, we can whittle away at the remaining symbols in this legacy
namespace with the eventual goal of removing them all. In the meantime,
this linter rule will prevent us from inadvertently importing new
symbols from core.
