attempt-4 gated every bare-type-reference site for VISIBILITY via a boolean
leak-check that only caught not-visible and DROPPED the ambiguous outcome, so two
DIRECT flat same-name type authors (the 0755/0105 ambiguity case) fell through to
a global findByName / struct_template_map pick at the non-leaf sites.
Unified author-outcome fix (one path, every site consumes it):
- flatTypeAuthorCount: ≥2 distinct flat authors that do NOT all collapse onto one
shared TypeId are now `.ambiguous` even when none carries a concrete TypeId yet —
two same-name GENERIC TEMPLATES (template name registered in no findByName slot)
are a genuine collision, exactly like two registered structs. Identical-target
authors (diamond import / two aliases onto the same target) still collapse to
`.one`, so all valid cases stay byte-identical.
- headTypeGate: the complete source-aware author outcome (.proceed / .resolved /
.ambiguous / .not_visible) for an unqualified bare TYPE head, emitting the loud
ambiguity diagnostic (consistent with the leaf / 0755) or the not-visible
diagnostic. headTypeLeak is now its poison-vs-proceed projection, so every head /
instantiation / alias-decl / match site poisons on ambiguity with the right
message. Reflection / type-arg and array/vector-literal identifier heads consume
`.resolved` to use the source-keyed TypeId, never a global findByName pick.
Regression examples/0767: size_of(Thing) / Nums.[1,2] / Box(s64) / t:Type=Thing /
case Thing: with two direct flat same-name authors each emit the ambiguity
diagnostic, exit 1 (fail-before on bb8f7dc: exit 0 / cascade). 0763/0764/0765/0766
/0755/0706/0544/0105 + FFI byte-identical. README: bare-type ambiguity is enforced
at every reference site.
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