feat(rendering): GPU architecture + visual quality fixes

M2 GPU instancing
- M2InstanceGPU SSBO (96 B/entry, double-buffered, 16384 max)
- Group opaque instances by (modelId, LOD); single vkCmdDrawIndexed per group
- boneBase field indexes into mega bone SSBO via gl_InstanceIndex

Indirect terrain drawing
- 24 MB mega index buffer (6M uint32) + 64 MB mega vertex buffer
- CPU builds VkDrawIndexedIndirectCommand per visible chunk
- Single VB/IB bind per frame; shadow pass reuses mega buffers
- Replaced vkCmdDrawIndexedIndirect with direct vkCmdDrawIndexed to fix
  host-mapped buffer race condition that caused terrain flickering

GPU frustum culling (compute shader)
- m2_cull.comp.glsl: 64-thread workgroups, sphere-vs-6-planes + distance cull
- CullInstanceGPU SSBO input, uint visibility[] output, double-buffered
- dispatchCullCompute() runs before main pass via render graph node

Consolidated bone matrix SSBOs
- 16 MB double-buffered mega bone SSBO (2048 instances × 128 bones)
- Eliminated per-instance descriptor sets; one megaBoneSet_ per frame
- prepareRender() packs bone matrices consecutively into current frame slot

Render graph / frame graph
- RenderGraph: RGResource handles, RGPass nodes, Kahn topological sort
- Automatic VkImageMemoryBarrier/VkBufferMemoryBarrier between passes
- Passes: minimap_composite, worldmap_composite, preview_composite,
  shadow_pass, reflection_pass, compute_cull
- beginFrame() uses buildFrameGraph() + renderGraph_->execute(cmd)

Pipeline derivatives
- PipelineBuilder::setFlags/setBasePipeline for VK_PIPELINE_CREATE_DERIVATIVE_BIT
- M2 opaque = base; alphaTest/alpha/additive are derivatives
- Applied to terrain (wireframe) and WMO (alpha-test) renderers

Rendering bug fixes:
- fix(shadow): compute lightSpaceMatrix before updatePerFrameUBO to eliminate
  one-frame lag that caused shadow trails and flicker on moving objects
- fix(shadow): scale depth bias with shadowDistance_ instead of hardcoded 0.8f
  to prevent acne at close range and gaps at far range
- fix(visibility): WMO group distance threshold 500u → 1200u to match terrain
  view distance; buildings were disappearing on the horizon
- fix(precision): camera near plane 0.05 → 0.5 (ratio 600K:1 → 60K:1),
  eliminating Z-fighting and improving frustum plane extraction stability
- fix(streaming): terrain load radius 4 → 6 tiles (~2133u → ~3200u) to exceed
  M2 render distance (2800u) and eliminate pop-in when camera turns;
  unload radius 7 → 9; spawn radius 3 → 4
- fix(visibility): ground-detail M2 distance multiplier 0.75 → 0.9 to reduce
  early pop of grass and debris

tools/asset_extract/extractor.cpp

@@ -537,20 +537,6 @@ static std::vector<ArchiveDesc> discoverArchives(const std::string& mpqDir,
     return result;
 }
 
-// Read a text file into a vector of lines (for external listfile loading)
-static std::vector<std::string> readLines(const std::string& path) {
-    std::vector<std::string> lines;
-    std::ifstream f(path);
-    if (!f) return lines;
-    std::string line;
-    while (std::getline(f, line)) {
-        // Trim trailing \r
-        if (!line.empty() && line.back() == '\r') line.pop_back();
-        if (!line.empty()) lines.push_back(std::move(line));
-    }
-    return lines;
-}
-
 // Extract the (listfile) from an MPQ archive into a set of filenames
 static void extractInternalListfile(HANDLE hMpq, std::set<std::string>& out) {
     HANDLE hFile = nullptr;
@@ -595,14 +581,9 @@ bool Extractor::enumerateFiles(const Options& opts,
 
     std::cout << "Found " << archives.size() << " MPQ archives\n";
 
-    // Load external listfile into memory once (avoids repeated file I/O)
-    std::vector<std::string> externalEntries;
-    std::vector<const char*> externalPtrs;
-    if (!opts.listFile.empty()) {
-        externalEntries = readLines(opts.listFile);
-        externalPtrs.reserve(externalEntries.size());
-        for (const auto& e : externalEntries) externalPtrs.push_back(e.c_str());
-        std::cout << "  Loaded external listfile: " << externalEntries.size() << " entries\n";
+    const bool haveExternalListFile = !opts.listFile.empty();
+    if (haveExternalListFile) {
+        std::cout << "  Using external listfile: " << opts.listFile << "\n";
     }
 
     const auto wantedDbcs = buildWantedDbcSet(opts);
@@ -616,12 +597,11 @@ bool Extractor::enumerateFiles(const Options& opts,
             continue;
         }
 
-        // Inject external listfile entries into archive's in-memory name table.
-        // SFileAddListFileEntries is fast — it only hashes the names against the
-        // archive's hash table, no file I/O involved.
-        if (!externalPtrs.empty()) {
-            SFileAddListFileEntries(hMpq, externalPtrs.data(),
-                                   static_cast<DWORD>(externalPtrs.size()));
+        // Inject external listfile into archive's in-memory name table.
+        // SFileAddListFile reads the file and hashes names against the
+        // archive's hash table.
+        if (haveExternalListFile) {
+            SFileAddListFile(hMpq, opts.listFile.c_str());
         }
 
         if (opts.verbose) {