Tidy reasampler_processor.h ceiling, restamp contour publish, tighten pitch-shift test bound

Splits BuiltCapture/sourceRateRefusalText into processor_snapshot.h; fixes stale lock-nesting notes; restamp now also publishes liveContours_ like reload; tightens a slack test bound and one drifted comment.

src/shell/instrument/instrument_bake.cpp

@@ -128,7 +128,7 @@ BakeChainResult runBake(ReaSamplerProcessor& processor) {
 
     // The snapshot comes first: the default program's window is derived from the sound it
     // carries (a Gate release, a Trigger play span), not from a constant.
-    ReaSamplerProcessor::BuiltCapture built = processor.bakeSnapshot(sampleRate);
+    BuiltCapture built = processor.bakeSnapshot(sampleRate);
     if (built.rateRefused) return fail("cannot render: " + sourceRateRefusalText());
     if (!built.sample) return fail("the loaded capture could not be decoded for the render");
     SampleData& snapshot = *built.sample;