test: replace fake and duplicate tests with real assertions

Fake tests rewritten to assert real behavior:
- audio_smoke: conversion tests now actually Convert() samples and verify
  output; waveform length/summary assertions tightened to exact values
- plugin_format_conversion: RowBytes/U8ToU16/LoadImageFile now call real
  production code (VideoParams::GetBytesPerPixel, sws scaler, OIIO decode
  of tests/img.png with known pixel values)
- core_color: HSV round trip now verifies fromHsv(toHsv(c)) == c instead
  of comparing toHsv against its own accessors
- core_bezier/node_inputimmediate: expected values replaced with
  independently derived constants instead of re-running the code under test
- common_commandlineparser/common_debug/common_jobtime: capture
  stdout/stderr/qDebug and assert actual output content
- proxy_manager: ProxyFinished test now drives a real proxy job instead of
  emitting the signal itself; proxy_dialog/panel/proxy/preferences/timeruler
  tests assert real widget state
- viewer_smoke/preview_autocacher/render_misc: zero-assertion tests given
  observable-state assertions or removed where nothing is observable

Duplicates removed:
- plugin_smoke_test.cpp: 18 tests duplicated from plugin_paraminstance /
  plugin_support_* / plugin_renderer_readback (751 -> 180 lines)
- module_smoke HumanStrings tests covered precisely by ui_humanstrings_test
- render_misc duplicate kDefaultInterpolation constant check

Removed by policy (skip allowed, never disabled):
- all DISABLED_ prefixes: re-enabled as real offscreen tests or deleted
- ffmpeg_decoder_hw: hardcoded personal path replaced with
  OAK_TEST_HW_DECODE_FILE env var, GTEST_SKIP when unset

Also:
- config_test: restore Config defaults after run (cross-test pollution)
- render_worker_footage: drop /tmp debug-output scaffolding
- previewaudiodevice construction test asserts the real bugfix

tests/gtest/common_qtutils_test.cpp

@@ -83,8 +83,11 @@ TEST(CommonQtUtils, QFontMetricsWidth)
 {
 	QFont font;
 	QFontMetrics fm(font);
-	int width = olive::QtUtils::QFontMetricsWidth(fm, QStringLiteral("Olive"));
-	EXPECT_GT(width, 0);
+	QString text = QStringLiteral("Olive");
+
+	// Thin wrapper: must forward to QFontMetrics::horizontalAdvance exactly
+	EXPECT_EQ(olive::QtUtils::QFontMetricsWidth(fm, text),
+			  fm.horizontalAdvance(text));
 }
 
 TEST(CommonQtUtils, CreateHorizontalLine)
@@ -117,8 +120,10 @@ TEST(CommonQtUtils, GetFormattedDateTime)
 {
 	QDateTime dt = QDateTime::fromString(QStringLiteral("2025-01-15T10:30:00"),
 										 Qt::ISODate);
-	QString s = olive::QtUtils::GetFormattedDateTime(dt);
-	EXPECT_FALSE(s.isEmpty());
+
+	// Qt::TextDate renders "ddd MMM d HH:mm:ss yyyy" in the C locale
+	EXPECT_EQ(olive::QtUtils::GetFormattedDateTime(dt),
+			  QStringLiteral("Wed Jan 15 10:30:00 2025"));
 }
 
 TEST(CommonQtUtils, WordWrapString)
@@ -126,15 +131,24 @@ TEST(CommonQtUtils, WordWrapString)
 	QFont font;
 	QFontMetrics fm(font);
 
-	// Use a moderate width; long words may not split cleanly, so just verify no crash
+	// A string wider than the bounding width must be split into
+	// multiple lines
 	QStringList wrapped = olive::QtUtils::WordWrapString(
 		QStringLiteral("hello world foo bar"), fm, 40);
-	EXPECT_GE(wrapped.size(), 1u);
+	EXPECT_GT(wrapped.size(), 1);
+
+	// A string that fits stays on a single line, untouched
+	wrapped = olive::QtUtils::WordWrapString(
+		QStringLiteral("hello world foo bar"), fm, 100000);
+	EXPECT_EQ(wrapped.size(), 1);
+	EXPECT_EQ(wrapped.first(), QStringLiteral("hello world foo bar"));
 
 	// Should preserve manual newlines
 	wrapped = olive::QtUtils::WordWrapString(QStringLiteral("line1\nline2"), fm,
 											 1000);
 	EXPECT_EQ(wrapped.size(), 2);
+	EXPECT_EQ(wrapped.at(0), QStringLiteral("line1"));
+	EXPECT_EQ(wrapped.at(1), QStringLiteral("line2"));
 }
 
 TEST(CommonQtUtils, ToQColorClampsValues)
@@ -149,13 +163,29 @@ TEST(CommonQtUtils, ToQColorClampsValues)
 
 TEST(CommonQtUtils, qHashRational)
 {
-	olive::core::rational r(3, 4);
-	EXPECT_NO_THROW(qHash(r));
+	using olive::core::rational;
+
+	// Hash contract: equal rationals must hash equally
+	EXPECT_EQ(qHash(rational(3, 4)), qHash(rational(3, 4)));
+	EXPECT_EQ(qHash(rational(3, 4)), qHash(rational(6, 8)));
+
+	// Distinct values must hash differently
+	EXPECT_NE(qHash(rational(3, 4)), qHash(rational(1, 2)));
+	EXPECT_NE(qHash(rational(1, 3)), qHash(rational(2, 3)));
 }
 
 TEST(CommonQtUtils, qHashTimeRange)
 {
-	olive::core::TimeRange tr(olive::core::rational(1),
-							  olive::core::rational(5));
-	EXPECT_NO_THROW(qHash(tr));
+	using olive::core::rational;
+	using olive::core::TimeRange;
+
+	// Hash contract: equal ranges must hash equally
+	EXPECT_EQ(qHash(TimeRange(rational(1), rational(5))),
+			  qHash(TimeRange(rational(1), rational(5))));
+
+	// Ranges differing in their in- or out-point must hash differently
+	EXPECT_NE(qHash(TimeRange(rational(1), rational(5))),
+			  qHash(TimeRange(rational(2), rational(5))));
+	EXPECT_NE(qHash(TimeRange(rational(1), rational(5))),
+			  qHash(TimeRange(rational(1), rational(6))));
 }