fix(managed): preserve malformed signature uncertainty in comparisons

Consume the signature producer status before inferring operand-resolution limits. Preserve exact byte-match provenance while malformed paired signatures remain unknown through current and historical Evidence, CLI and MCP.

docs/managed-code-analysis.md

@@ -544,7 +544,11 @@ establish which library the runtime loaded.
 
 Signatures retain their decoded fields, but a Field or MethodDef row whose
 signature has the other member kind is malformed and cannot establish an
-unchanged signature. Runtime-provided methods are counted separately in
+unchanged signature. Comparison retains exact byte-based pairs for malformed
+signatures, including empty, truncated, or invalid headers, but reports them as
+unknown with a `signature-malformed` limitation when no change is observed.
+This applies to historical Evidence without signature-resolution attestation as
+well. Runtime-provided methods are counted separately in
 `native_implementations.runtime_provided`; they have no file-backed native body
 for this workflow to map and do not increase `native_body_unresolved`. Historical
 verification Evidence without this separate count leaves it unknown (`null`).