Don't use UNUSED2 on always unused variables

Not introducing a variable enforces that the variable is not used.
`UNUSED2` on the other hand is used to silence the warning.

source/graphics/Unit.cpp

@@ -53,9 +53,7 @@ CUnit::~CUnit()
 
 std::unique_ptr<CUnit> CUnit::Create(const CStrW& actorName, const entity_id_t id, const uint32_t seed, CObjectManager& objectManager)
 {
-	auto [success, actor] = objectManager.FindActorDef(actorName);
-
-	UNUSED2(success);
+	const CActorDef& actor{std::get<1>(objectManager.FindActorDef(actorName))};
 
 	std::unique_ptr<CUnit> unit{new CUnit(objectManager, actor, id, seed)};
 	if (!unit->m_Model)

source/lib/sysdep/os/unix/unix.cpp

@@ -274,12 +274,8 @@ ErrorReactionInternal sys_display_error(const wchar_t* text, size_t flags)
 }
 
 
-Status sys_StatusDescription(int err, wchar_t* buf, size_t max_chars)
+Status sys_StatusDescription(int /*err*/, wchar_t* /*buf*/, size_t /*max_chars*/)
 {
-	UNUSED2(err);
-	UNUSED2(buf);
-	UNUSED2(max_chars);
-
 	// don't need to do anything: lib/errors.cpp already queries
 	// libc's strerror(). if we ever end up needing translation of
 	// e.g. Qt or X errors, that'd go here.

source/lib/sysdep/os/win/wposix/waio.cpp

@@ -566,11 +566,10 @@ int aio_write(struct aiocb* cb)
 	return Issue(cb);
 }
 
-
-int lio_listio(int mode, struct aiocb* const cbs[], int n, struct sigevent* se)
+// Signaling is not implemented.
+int lio_listio(int mode, struct aiocb* const cbs[], int n, struct sigevent* /*se*/)
 {
 	ENSURE(mode == LIO_WAIT || mode == LIO_NOWAIT);
-	UNUSED2(se);	// signaling is not implemented.
 
 	for(int i = 0; i < n; i++)
 	{

source/ps/ProfileViewer.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2022 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -119,7 +119,7 @@ public:
 	 *
 	 * @return true if the row should be highlighted in a special color.
 	 */
-	virtual bool IsHighlightRow(size_t row) { UNUSED2(row); return false; }
+	virtual bool IsHighlightRow(size_t /*row*/) { return false; }
 };
 
 

source/renderer/backend/gl/ShaderProgram.cpp

@@ -675,11 +675,8 @@ public:
 
 		m_Program = 0;
 		m_FileDependencies = {programPath};
-		for (const auto& [path, type] : shaderStages)
-		{
-			UNUSED2(type);
-			m_FileDependencies.emplace_back(path);
-		}
+		for (const auto& shaderStage : shaderStages)
+			m_FileDependencies.emplace_back(std::get<0>(shaderStage));
 
 		// TODO: replace by scoped bind.
 		m_Device->GetActiveCommandContext()->SetGraphicsPipelineState(

source/renderer/backend/vulkan/DeviceCommandContext.cpp

@@ -608,9 +608,9 @@ void CDeviceCommandContext::BeginFramebufferPass(IFramebuffer* framebuffer)
 			m_Framebuffer->GetDepthStencilAttachmentLoadOp() == AttachmentLoadOp::CLEAR);
 	if (needsClearValues)
 	{
-		for (CTexture* colorAttachment : m_Framebuffer->GetColorAttachments())
+		const CFramebuffer::ColorAttachments& colorAttachments{m_Framebuffer->GetColorAttachments()};
+		std::for_each(colorAttachments.begin(), colorAttachments.end(), [&](CTexture*)
 		{
-			UNUSED2(colorAttachment);
 			const CColor& clearColor = m_Framebuffer->GetClearColor();
 			// The four array elements of the clear color map to R, G, B, and A
 			// components of image formats, in order.
@@ -619,7 +619,7 @@ void CDeviceCommandContext::BeginFramebufferPass(IFramebuffer* framebuffer)
 			clearValues.back().color.float32[1] = clearColor.g;
 			clearValues.back().color.float32[2] = clearColor.b;
 			clearValues.back().color.float32[3] = clearColor.a;
-		}
+		});
 		if (m_Framebuffer->GetDepthStencilAttachment())
 		{
 			clearValues.emplace_back();

source/simulation2/components/CCmpVisualActor.cpp

@@ -496,12 +496,12 @@ public:
 			m_Unit->GetAnimation()->SetAnimationSyncOffset(m_AnimSyncOffsetTime.ToFloat());
 	}
 
-	void SetShadingColor(fixed r, fixed g, fixed b, fixed a) override
+	// TODO: Why is `a` even an argument?
+	void SetShadingColor(fixed r, fixed g, fixed b, fixed /*a*/) override
 	{
 		m_R = r;
 		m_G = g;
 		m_B = b;
-		UNUSED2(a); // TODO: why is this even an argument?
 
 		if (m_Unit)
 		{

source/soundmanager/SoundManager.cpp

@@ -664,23 +664,20 @@ void CSoundManager::PlayAsGroup(const VfsPath& groupPath, const CVector3D& sourc
 		group->PlayNext(sourcePos, source);
 }
 
-void CSoundManager::PlayAsMusic(const VfsPath& itemPath, bool looping)
+void CSoundManager::PlayAsMusic(const VfsPath& itemPath, bool /*looping*/)
 {
 	if (m_Enabled)
 	{
-		UNUSED2(looping);
-
 		ISoundItem* aSnd = LoadItem(itemPath);
 		if (aSnd != NULL)
 			SetMusicItem(aSnd);
 	}
 }
 
-void CSoundManager::PlayAsAmbient(const VfsPath& itemPath, bool looping)
+void CSoundManager::PlayAsAmbient(const VfsPath& itemPath, bool /*looping*/)
 {
 	if (m_Enabled)
 	{
-		UNUSED2(looping);
 		ISoundItem* aSnd = LoadItem(itemPath);
 		if (aSnd != NULL)
 			SetAmbientItem(aSnd);

source/soundmanager/items/CSoundBase.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2022 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -57,9 +57,8 @@ void CSoundBase::ReleaseOpenAL()
 	}
 }
 
-void CSoundBase::Attach(CSoundData* itemData)
+void CSoundBase::Attach(CSoundData* /*itemData*/)
 {
-	UNUSED2(itemData);
 }
 
 void CSoundBase::ResetVars()