Review follow-up to the ARCH-B split (comment/import hygiene only, no
code changes):
- Section banners that travelled to the wrong file with the B1-B8 cuts
are reworded to describe the section that actually follows (e.g.
stmt.zig's trailing "Expression lowering", expr.zig's "Control flow"
before lowerChainedComparison) or deleted where nothing follows
(4 trailing-at-EOF banners). ffi.zig's facade note no longer claims
the IMP builders "stay here" (they live in lower/objc_class.zig);
protocol.zig's namespace-lookup banner now points at
pack.zig:resolvePackProjection for the orchestrator.
- lower.zig's two lower/expr.zig alias blocks (B8.1 + B8.2 appends)
merged into one.
- 448 unused header decls pruned from the 15 lower/*.zig files (each
had inherited lower.zig's full import block; pruned to fixpoint so
cascading type-extraction consts went too).
Gate: zig build OK; zig build test 426/426; run_examples 541/0; zero
expected/ snapshot churn.
Verbatim relocation of the 13-method protocol cluster (protocol decl
registration, param-protocol instantiation, thunk creation, vtable
globals, protocol-value construction, dispatch emission, impl lookup)
into src/ir/lower/protocol.zig. 13 fn aliases on Lowering keep all call
sites unchanged.
Two pub nested types travelled with the run (ProjectionPosition,
PackProjection) and are re-exposed via Lowering type aliases; they are
pack-domain types and may relocate to lower/pack.zig in B7.2.
Method pub-flips: allocViaContext, callForeign, genericInstanceMethod,
monomorphizeFunction.
Gate: zig build OK; zig build test 426/426; run_examples 541/0; zero
expected/ snapshot churn.
