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)

tools/fix_bundle_vcxproj_paths.py

@@ -0,0 +1,126 @@
+#!/usr/bin/env python3
+# Rewrite vcxproj files in *-bundle directories to use direct relative paths
+# to the vendor submodule, removing the dependency on POSIX symlinks.
+#
+# Usage: python3 tools/fix_bundle_vcxproj_paths.py [--dry-run]
+#
+# Before this script the vcxproj paths were:
+#   ..\..\..\..\C\         (4 levels = bundle root, then symlink)
+#   ..\..\..\Common\       (3 levels = bundle CPP, then symlink)
+#   ..\..\Archive\         (2 levels = bundle 7zip, then symlink)
+#
+# After this script (same as versions/zstd bundle):
+#   ..\..\..\..\..\VER\C\                (5 levels = versions/, then vendor)
+#   ..\..\..\..\..\VER\CPP\Common\       (5 levels)
+#   ..\..\..\..\..\VER\CPP\7zip\Archive\ (5 levels)
+#
+# UI\NSIS paths are kept as-is (real bundle files, no symlink needed).
+
+import re
+import os
+import sys
+
+bs = "\\"
+
+BUNDLES = {
+    "25.01": "versions/25.01-bundle/CPP/7zip/Bundles/Nsis7z",
+    "26.00": "versions/26.00-bundle/CPP/7zip/Bundles/Nsis7z",
+    "26.01": "versions/26.01-bundle/CPP/7zip/Bundles/Nsis7z",
+}
+
+
+def fix_path(path, v7z, vcpp, vc):
+    """Rewrite a single Include= path value."""
+    p = path
+    # depth-4: ..\..\..\..\  → vendor root
+    prefix4 = bs.join([".."] * 4) + bs
+    if p.startswith(prefix4):
+        rest = p[len(prefix4):]
+        # C\ or C
+        if rest.startswith("C" + bs) or rest == "C":
+            suffix = rest[2:] if rest.startswith("C" + bs) else ""
+            return vc + (bs + suffix if suffix else "")
+        # generic (shouldn't appear, but handle gracefully)
+        return vcpp + bs + ".." + bs + rest
+    # depth-3: ..\..\..\ → vendor CPP
+    prefix3 = bs.join([".."] * 3) + bs
+    if p.startswith(prefix3):
+        rest = p[len(prefix3):]
+        return vcpp + bs + rest
+    # depth-2: ..\..\ → vendor CPP\7zip\  (except UI\NSIS which stays)
+    prefix2 = bs.join([".."] * 2) + bs
+    if p.startswith(prefix2):
+        rest = p[len(prefix2):]
+        if rest.startswith("UI" + bs + "NSIS"):
+            return path  # bundle-local real file
+        return v7z + bs + rest
+    # depth-0: local bundle file
+    return path
+
+
+def transform_file(fpath, ver, dry_run):
+    vendor  = bs.join([".."] * 5) + bs + ver
+    v7z     = vendor + bs + "CPP" + bs + "7zip"
+    vcpp    = vendor + bs + "CPP"
+    vc      = vendor + bs + "C"
+    old_inc = bs.join([".."] * 3) + bs + ";"
+
+    with open(fpath, "rb") as f:
+        raw = f.read()
+    # Detect BOM
+    bom = b"\xef\xbb\xbf" if raw.startswith(b"\xef\xbb\xbf") else b""
+    content = raw.lstrip(b"\xef\xbb\xbf").decode("utf-8")
+
+    lines = content.splitlines(keepends=True)
+    out = []
+    changed = 0
+
+    for line in lines:
+        orig = line
+
+        # Fix AdditionalIncludeDirectories
+        if "<AdditionalIncludeDirectories>" in line:
+            # Remove spurious trailing space before semicolon
+            line = re.sub(r"(\.\.[/\\]\.\.)[/\\]\s+;", r"\1" + bs + ";", line)
+            # Replace "..\..\..\;" with vendor paths
+            if old_inc in line:
+                new_inc = vcpp + bs + ";" + vendor + bs + ";" + old_inc
+                line = line.replace(old_inc, new_inc)
+
+        # Fix ClCompile / ClInclude Include paths
+        m = re.search(r'(Include=")([^"]+)(")', line)
+        if m and ("<ClCompile" in line or "<ClInclude" in line):
+            newpath = fix_path(m.group(2), v7z, vcpp, vc)
+            if newpath != m.group(2):
+                line = line[: m.start()] + m.group(1) + newpath + m.group(3) + line[m.end():]
+
+        if line != orig:
+            changed += 1
+        out.append(line)
+
+    new_content = "".join(out)
+    print(f"  {os.path.basename(fpath)}: {changed} lines changed")
+    if not dry_run and changed > 0:
+        with open(fpath, "wb") as f:
+            f.write(bom + new_content.encode("utf-8"))
+
+
+def main():
+    dry_run = "--dry-run" in sys.argv
+    root = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+    if dry_run:
+        print("DRY RUN — no files will be written\n")
+
+    for ver, rel_dir in BUNDLES.items():
+        bundle_dir = os.path.join(root, rel_dir)
+        print(f"version {ver}:")
+        for fname in ["Nsis7z.vcxproj", "Nsis7z_vs2026.vcxproj"]:
+            fpath = os.path.join(bundle_dir, fname)
+            if not os.path.exists(fpath):
+                print(f"  {fname}: SKIP (not found)")
+                continue
+            transform_file(fpath, ver, dry_run)
+
+
+if __name__ == "__main__":
+    main()