Ψ-W3 remediation: fix the verify doc's wrong render source, add missing content checks, soften unverified claims

Corrected the Render-dialog source name the refusal's evidence depends on, added a by-ear content check and a file-size channel proxy, and stopped two comments from overclaiming.

tests/test_wav_codec.cpp

@@ -779,7 +779,9 @@ static void testCollapsePreservesQuietNaNBitPattern() {
 // identically to "the channels differ" — a stereo file landing under a plain Ok. The
 // report is where they must part: Declined stays silent (a capture with nothing to
 // collapse reads as it always did), and the other two say different things.
-static void testCollapseOutcomesReportDistinctly() {
+// Pins the three suffix STRINGS, not user-observable behavior — see wav_codec.h's
+// monoCollapseSuffix doc: this text reaches no one on a successful capture.
+static void testCollapseOutcomeSuffixesAreDistinctStrings() {
     const std::string declined  = monoCollapseSuffix(MonoCollapseOutcome::Declined);
     const std::string collapsed = monoCollapseSuffix(MonoCollapseOutcome::Collapsed);
     const std::string failed    = monoCollapseSuffix(MonoCollapseOutcome::Failed);
@@ -828,7 +830,7 @@ int main() {
     testCollapseDeclinesOnUnparseableBytes();
     testCollapseChangesContentHash();
     testCollapsePreservesQuietNaNBitPattern();
-    testCollapseOutcomesReportDistinctly();
+    testCollapseOutcomeSuffixesAreDistinctStrings();
 
     if (g_fail == 0) std::printf("wav_codec: all tests passed\n");
     else             std::printf("wav_codec: %d CHECK(s) FAILED\n", g_fail);