Fix vacuous bounds test and stale/circular comments from the settle

Replace the self-comparing render-window loop with a genuinely discriminating
floor-vs-exact check; correct two stale claims; mark the Auto/Manual floor-parity
premise as unverified; drop the STARTPOS/ENDPOS comment's circular justification.

tests/test_render_settings.cpp

@@ -65,9 +65,11 @@ static void testRealtimeIsUnsupportedOffline() {
 }
 
 static void testEveryRenderSourceLabelIsPinnedVerbatim() {
-    // docs/VERIFICATION.md asks Daniel to report the refusal's `Render source:` line
-    // back verbatim, so every label is pinned to its literal — a typo in any of them
-    // breaks the report that quotes it, and only a literal catches that.
+    // docs/VERIFICATION.md's short-render bullet asks Daniel to report the refusal
+    // line back verbatim, and that line always carries the render source
+    // (render_bounds_gate.cpp appends "Render source: <label>."), so every label
+    // is pinned to its literal — a typo in any of them breaks the report that
+    // quotes it, and only a literal catches that.
     CHECK(std::strcmp(renderSourceLabel(SourceMode::MasterMix), "master mix") == 0);
     CHECK(std::strcmp(renderSourceLabel(SourceMode::TimeSelection), "master mix") == 0);
     CHECK(std::strcmp(renderSourceLabel(SourceMode::SelectedTracks),
@@ -81,9 +83,10 @@ static void testEveryRenderSourceLabelIsPinnedVerbatim() {
 static void testLabelsSeparateExactlyWhatTheRenderSeparates() {
     // The labels partition the offline modes the way RENDER_SETTINGS does, and no
     // finer: same bits => same words (MasterMix/TimeSelection both render the master
-    // mix, custom-time-bounded), different bits => different words. Naming two modes
-    // apart that render identically would put a distinction in a bug report that does
-    // not exist in the render.
+    // mix, unqualified — both hand their window over the same time-selection bounds
+    // mode), different bits => different words. Naming two modes apart that render
+    // identically would put a distinction in a bug report that does not exist in
+    // the render.
     const SourceMode offline[] = {
         SourceMode::MasterMix, SourceMode::TimeSelection, SourceMode::SelectedTracks,
         SourceMode::SelectedItems, SourceMode::RazorArea,

tests/test_render_window.cpp

@@ -408,14 +408,17 @@ static void testOnAndOffGridWindowsAreHonoredIdentically() {
     CHECK(on  == 48000);
     CHECK(off == 48000);
 
-    // The discriminating half: the off-grid window is one a flooring render WOULD get
-    // wrong (47992 against 48000) while the on-grid one is untouched by a floor. The
-    // gate's verdict must not notice that difference at any delta.
-    CHECK(msFlooredEndFrameCount(offStart, offEnd, 48000) == 47992);
-    CHECK(msFlooredEndFrameCount(onStart,  onEnd,  48000) == on);
-    for (long long delta = -3; delta <= 3; ++delta)
-        CHECK(renderHonoredBounds(on, on + delta) ==
-              renderHonoredBounds(off, off + delta));
+    // The discriminating half: a render that landed the FLOORED count would be
+    // refused on the off-grid window (47992 against the required 48000, an
+    // 8-frame gap) but honored on the on-grid one, where flooring changes
+    // nothing. If the floor ever came back on the settled path, this is what
+    // would start failing.
+    const long long offFloored = msFlooredEndFrameCount(offStart, offEnd, 48000);
+    const long long onFloored  = msFlooredEndFrameCount(onStart,  onEnd,  48000);
+    CHECK(offFloored == 47992);
+    CHECK(onFloored  == on);
+    CHECK(!renderHonoredBounds(off, offFloored));
+    CHECK(renderHonoredBounds(on, onFloored));
 }
 
 static void testOnAndOffGridAt44100WhereAMillisecondIsNotWholeFrames() {
@@ -428,11 +431,14 @@ static void testOnAndOffGridAt44100WhereAMillisecondIsNotWholeFrames() {
     const long long off = frameCountFor(offStart, offEnd, 44100);
     CHECK(on  == 44100);
     CHECK(off == 44100);
-    CHECK(msFlooredEndFrameCount(offStart, offEnd, 44100) == 44092);
-    CHECK(msFlooredEndFrameCount(onStart,  onEnd,  44100) == on);
-    for (long long delta = -3; delta <= 3; ++delta)
-        CHECK(renderHonoredBounds(on, on + delta) ==
-              renderHonoredBounds(off, off + delta));
+    const long long offFloored = msFlooredEndFrameCount(offStart, offEnd, 44100);
+    const long long onFloored  = msFlooredEndFrameCount(onStart,  onEnd,  44100);
+    CHECK(offFloored == 44092);
+    CHECK(onFloored  == on);
+    // Same discriminating pair as the 48 kHz case: the floor would be caught
+    // off-grid and invisible on-grid, even where the grid itself isn't frame-aligned.
+    CHECK(!renderHonoredBounds(off, offFloored));
+    CHECK(renderHonoredBounds(on, onFloored));
 }
 
 int main() {