capture: state the bounds tolerance as empirical, refuse unmeasurable renders, keep refused ones for diagnosis

The one-frame bound is not provable for a per-edge renderer; the test now shows where it breaks. Refused renders move out of the bank instead of being deleted, so the DAW experiment has something to read.

tests/test_render_settings.cpp

@@ -64,26 +64,49 @@ static void testRealtimeIsUnsupportedOffline() {
     CHECK(!renderSettingsFor(SourceMode::Realtime, 1.0).supported);
 }
 
-static void testEveryRenderSourceIsNameable() {
-    // The bounds refusal quotes this label to say WHICH render source missed the
-    // window, so every mode must name itself and no two may read alike.
-    const SourceMode all[] = {
-        SourceMode::MasterMix, SourceMode::TimeSelection, SourceMode::SelectedTracks,
-        SourceMode::SelectedItems, SourceMode::RazorArea, SourceMode::Realtime,
-    };
-    for (std::size_t i = 0; i < sizeof(all) / sizeof(all[0]); ++i) {
-        const char* label = renderSourceLabel(all[i]);
-        CHECK(label != nullptr && label[0] != '\0');
-        CHECK(std::strcmp(label, "unknown") != 0);
-        for (std::size_t j = i + 1; j < sizeof(all) / sizeof(all[0]); ++j)
-            CHECK(std::strcmp(label, renderSourceLabel(all[j])) != 0);
-    }
-    // The two the refusal must tell apart: a source that derives its own bounds vs
-    // the time-bounded render.
-    CHECK(std::strcmp(renderSourceLabel(SourceMode::SelectedItems),
-                      "selected media items") == 0);
+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.
+    CHECK(std::strcmp(renderSourceLabel(SourceMode::MasterMix), "master mix") == 0);
+    CHECK(std::strcmp(renderSourceLabel(SourceMode::TimeSelection), "master mix") == 0);
     CHECK(std::strcmp(renderSourceLabel(SourceMode::SelectedTracks),
                       "selected tracks via master") == 0);
+    CHECK(std::strcmp(renderSourceLabel(SourceMode::SelectedItems),
+                      "selected media items") == 0);
+    CHECK(std::strcmp(renderSourceLabel(SourceMode::RazorArea), "razor edits") == 0);
+    CHECK(std::strcmp(renderSourceLabel(SourceMode::Realtime), "realtime record") == 0);
+}
+
+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.
+    const SourceMode offline[] = {
+        SourceMode::MasterMix, SourceMode::TimeSelection, SourceMode::SelectedTracks,
+        SourceMode::SelectedItems, SourceMode::RazorArea,
+    };
+    constexpr std::size_t n = sizeof(offline) / sizeof(offline[0]);
+    for (std::size_t i = 0; i < n; ++i) {
+        const char* label = renderSourceLabel(offline[i]);
+        CHECK(label != nullptr && label[0] != '\0');
+        CHECK(std::strcmp(label, "unknown") != 0);
+        CHECK(renderSettingsFor(offline[i], 1.0).supported);
+        for (std::size_t j = i + 1; j < n; ++j) {
+            const bool sameRender = renderSettingsFor(offline[i], 1.0).settings ==
+                                    renderSettingsFor(offline[j], 1.0).settings;
+            const bool sameLabel =
+                std::strcmp(label, renderSourceLabel(offline[j])) == 0;
+            CHECK(sameRender == sameLabel);
+        }
+    }
+    // Realtime is not an offline render source at all, so it names its own mechanism
+    // rather than a RENDER_SETTINGS value — outside the partition above by design.
+    CHECK(!renderSettingsFor(SourceMode::Realtime, 1.0).supported);
+    CHECK(std::strcmp(renderSourceLabel(SourceMode::Realtime),
+                      renderSourceLabel(SourceMode::MasterMix)) != 0);
 }
 
 // --- tail: TailMode -> RENDER_* mapping (docs/product/capture-tail.md) --------
@@ -418,7 +441,8 @@ int main() {
     testSelectedItemsSingleFile();
     testRazorSingleFile();
     testRealtimeIsUnsupportedOffline();
-    testEveryRenderSourceIsNameable();
+    testEveryRenderSourceLabelIsPinnedVerbatim();
+    testLabelsSeparateExactlyWhatTheRenderSeparates();
     testTailNoneIsExactBounds();
     testTailAutoIsSurgicalTrim();
     testAutoTrimRatioDerivesFromDb();