refactor: replace bundle symlinks with direct vendor paths in vcxproj

Windows builds now use direct relative paths to the vendor submodules
(same pattern as versions/zstd bundle) instead of relying on POSIX
symlinks that git cannot materialise correctly on Windows without
Developer Mode / core.symlinks=true.

Changes:
- Remove all 66 symlinks from each of 25.01-bundle, 26.00-bundle,
  26.01-bundle (198 total).  POSIX symlinks are still created on Linux
  by setup_bundle_symlinks.py for the GNU make builds.
- Update Nsis7z.vcxproj / Nsis7z_vs2026.vcxproj in all three bundles:
    depth-4  ..\..\..\..\C\  ->  ..\..\..\..\..\VER\C    depth-3  ..\..\..\{Common,Windows}\  ->  ..\..\..\..\..\VER\CPP\{...}    depth-2  (non-NSIS)  ->  ..\..\..\..\..\VER\CPP\7zip\...
    UI\NSIS paths unchanged (real bundle files)
    AdditionalIncludeDirectories patched to point at vendor CPP/
- Add tools/fix_bundle_vcxproj_paths.py (idempotent helper used to
  perform the rewrite; kept for future reference / re-runs)

versions/26.01-bundle/CPP/7zip/UI/Agent

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/Agent

versions/26.01-bundle/CPP/7zip/UI/Client7z

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/Client7z

versions/26.01-bundle/CPP/7zip/UI/Common

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/Common

versions/26.01-bundle/CPP/7zip/UI/Console

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/Console

versions/26.01-bundle/CPP/7zip/UI/Explorer

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/Explorer

versions/26.01-bundle/CPP/7zip/UI/Far

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/Far

versions/26.01-bundle/CPP/7zip/UI/FileManager

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/FileManager

versions/26.01-bundle/CPP/7zip/UI/GUI

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/GUI

versions/26.01-bundle/CPP/7zip/UI/makefile

@@ -1 +0,0 @@
-../../../../26.01/CPP/7zip/UI/makefile