Delete module_fns as a separate function-author fact source. Its authors
already live in the module_decls raw facts, so lowerRetainedSameNameAuthors now
reads function authors straight out of module_decls (filtered to *FnDecl via
fnDeclOfRaw) — the same path → name → RawDeclRef store, fn-filtered. Remove
imports.ModuleFns / FnIndex / indexModuleFns / buildModuleFns / fnDeclOf, the
Compilation.module_fns field + its build + wiring, and ProgramIndex.module_fns.
Remove VisibilityMode.legacy_direct_any (the quarantined own-scope-plus-full-
import_graph mode): no production caller passed it, so the collectVisibleAuthors
and isVisible switch arms that handled it are dead and go too, collapsing
VisEdgeSet to the single flat-import walk. No semantic fallback is introduced;
import_graph stays the transitive-visibility source for findVisibleImpls.
Additive: the old maps stay active and lowering still consumes them — no
lowering consumer is cut over to the DeclTable (that is S3), and no resolution
behavior changes. Tests that drove the removed symbols are rerouted through
module_decls / the flat-edge walk.
Gate over the baseline-green corpus: zig build, zig build test (424/424),
bash tests/run_examples.sh (540 passed) — all exit 0; single-author output
byte-identical; multi-author 0722–0740 stdout/exit unchanged.
cd7510067f