[GPU] log_draws: also dump vertex positions for file correlation

Extend the RE draw-logger to dump the first few vertex POSITIONS (read
from guest memory) under each draw. The f32 position bytes are identical
between the guest buffer and the on-disc .xpr (only f16 pairs are
rearranged on load), so these values can be grep'd for in a resource file
to locate a mesh whose in-file offset is otherwise unknown.

Validated: world-space stage geometry byte-matches Stage_*.xpr at exact
offsets. (Load-time-transformed meshes like the player ship don't match,
which is itself a useful finding.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/xenia/gpu/command_processor.cc

@@ -215,6 +215,51 @@ void CommandProcessor::LogDrawForRE(uint32_t vgt_draw_initiator_value,
             a.stride, a.is_signed ? 1 : 0, a.is_integer ? 1 : 0, a.exp_adjust);
       }
     }
+
+    // Dump the first few vertex POSITIONS from guest memory. The f32 position
+    // bytes are identical between the guest buffer and the on-disc .xpr (only
+    // f16 pairs are rearranged on load), so these values can be searched for in
+    // the file to locate a mesh whose in-file offset is otherwise unknown
+    // (e.g. multi-XBG7 body meshes). See docs/re/structures/xbg7-mesh.md.
+    if (!vs->vertex_bindings().empty()) {
+      const auto& binding = vs->vertex_bindings()[0];
+      xenos::xe_gpu_vertex_fetch_t fetch =
+          register_file_->GetVertexFetch(binding.fetch_constant);
+      // Position = the first f32×3 attribute (offset is in dwords).
+      int32_t pos_off_bytes = -1;
+      for (const auto& attr : binding.attributes) {
+        if (attr.fetch_instr.attributes.data_format ==
+            xenos::VertexFormat::k_32_32_32_FLOAT) {
+          pos_off_bytes = attr.fetch_instr.attributes.offset * 4;
+          break;
+        }
+      }
+      uint32_t stride = binding.stride_words * 4;
+      uint32_t vbase = uint32_t(fetch.address) << 2;
+      uint32_t buf_bytes = uint32_t(fetch.size) * 4;
+      if (pos_off_bytes >= 0 && stride > 0) {
+        uint32_t max_v = buf_bytes / stride;
+        uint32_t n = max_v < 8 ? max_v : 8;
+        re_out << "  positions:";
+        for (uint32_t v = 0; v < n; ++v) {
+          uint32_t a = vbase + v * stride + uint32_t(pos_off_bytes);
+          const uint8_t* p = memory_->TranslatePhysical<const uint8_t*>(a);
+          if (!p) {
+            break;
+          }
+          auto be_f32 = [](const uint8_t* q) {
+            uint32_t w = (uint32_t(q[0]) << 24) | (uint32_t(q[1]) << 16) |
+                         (uint32_t(q[2]) << 8) | uint32_t(q[3]);
+            float f;
+            std::memcpy(&f, &w, 4);
+            return f;
+          };
+          re_out << fmt::format(" ({:.4f},{:.4f},{:.4f})", be_f32(p),
+                                be_f32(p + 4), be_f32(p + 8));
+        }
+        re_out << "\n";
+      }
+    }
   } else {
     re_out << "  (vertex shader not analyzed yet)\n";
   }