feat(25.01): add bundle wrapper directory with NSIS sources and vendor symlinks

Mirror the 26.00-bundle / 26.01-bundle approach for 25.01:

- versions/25.01-bundle/CPP/7zip/Bundles/Nsis7z/: project-owned NSIS plugin
  wrapper sources (api.h, nsis7z.cpp, pluginapi.*, resource.*, StdAfx*,
  Nsis7z.sln, Nsis7z.vcxproj, Nsis7z.vcxproj.filters, Nsis7z_vs2026.vcxproj).
- versions/25.01-bundle/CPP/7zip/UI/NSIS/: NSIS UI sources; StdAfx.h patched
  to use relative include path and MinGW-compatible Windows.h guard (the
  upstream 25.01 file used an absolute path incompatible with the bundle layout).
- versions/25.01-bundle/CPP/7zip/LzmaDec_gcc.mak: forwarding stub.
- versions/25.01-bundle/{C,Asm} and CPP sub-trees: symlinks into versions/25.01/.
- tools/linux/setup_25_01_bundle_symlinks.py: idempotent symlink-recreation script.

tools/linux/setup_25_01_bundle_symlinks.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+"""Creates symlinks in versions/25.01-bundle to mirror vendor directory structure."""
+import os
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+bundle_root = ROOT / "versions/25.01-bundle"
+vendor_root = ROOT / "versions/25.01"
+bundle_7zip = bundle_root / "CPP/7zip"
+vendor_7zip = vendor_root / "CPP/7zip"
+bundle_cpp  = bundle_root / "CPP"
+vendor_cpp  = vendor_root / "CPP"
+
+# Root-level symlinks: C and Asm
+for name in ("C", "Asm"):
+    target = bundle_root / name
+    if not target.exists() and not target.is_symlink():
+        rel = os.path.relpath(vendor_root / name, bundle_root)
+        os.symlink(rel, target)
+        print(f"  symlink: {target.relative_to(ROOT)} -> {rel}")
+
+for item in vendor_7zip.iterdir():
+    target = bundle_7zip / item.name
+    if not target.exists() and not target.is_symlink():
+        rel = os.path.relpath(item, bundle_7zip)
+        os.symlink(rel, target)
+        print(f"  symlink: {target.relative_to(ROOT)} -> {rel}")
+
+bundle_ui = bundle_7zip / "UI"
+vendor_ui = vendor_7zip / "UI"
+bundle_ui.mkdir(exist_ok=True)
+for item in vendor_ui.iterdir():
+    target = bundle_ui / item.name
+    if not target.exists() and not target.is_symlink():
+        rel = os.path.relpath(item, bundle_ui)
+        os.symlink(rel, target)
+        print(f"  symlink: {target.relative_to(ROOT)} -> {rel}")
+
+for item in vendor_cpp.iterdir():
+    if item.name == "7zip":
+        continue
+    target = bundle_cpp / item.name
+    if not target.exists() and not target.is_symlink():
+        rel = os.path.relpath(item, bundle_cpp)
+        os.symlink(rel, target)
+        print(f"  symlink: {target.relative_to(ROOT)} -> {rel}")
+
+print("Done")