Add the strict pmacs.statusline provider registry, deterministic
borrow-released per-window evaluation, context-scoped failure latches,
and a pure built-in LSP provider.
Preserve the legacy TUI modeline while composing faced custom runs,
and append authoritative complete StatuslineSegments replacements for
semantic frontends. Expand dynamic ThemeFacts, reset producer/frontend
baselines symmetrically, and gate all provider work off protocol v18.
Teach the GPU to atomically validate, resolve, shape, clip, and cache
custom modeline runs without displacing the protected status suffix.
Document the public Lua lifecycle, wire ownership, snapshot semantics,
and the fully gated Arc 4 stage-3 delivery state.
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>