`committed_edit_keeps_diff_line_backgrounds` passed alone and
single-threaded but failed under parallel execution, so the workspace
gate was red.
`terminal_native_lock_paints_only_native_colors` engages the
process-global terminal-native lock. While it is held `Theme::current()`
returns `terminal_default()`, whose `diff_*_bg` are all `Color::Reset`,
so no band is painted at all — and `current_kind()` reports a nominal
`KigiNight`, which is what made the failure read as a theme mismatch.
Two changes, both at the cause:
- hold the shared theme lock via `theme_cache::pin_theme()`, the helper
written for this and until now unused, so the lock cannot be engaged
mid-test
- assert the invariant (two distinct non-Reset bands) instead of exact
RGB: the entry line cache is keyed on the GLOBAL theme kind, so an
exact-color assertion races by construction. Span-level colors stay
pinned by the `tool::edit` tests that own them
The failure message now reports the theme, height, and the bands it
actually found, which is how the cause was located.
ZacharyZhang-NY
74402f3078