feat(build): add --dist to all remaining legacy Windows build scripts

Same --dist redirect (output to <repo>/dist/<config> instead of
plugins/<config>) applied to every per-version Windows script so the
flag works regardless of --7zip-version/--toolset the dispatcher
selects. Mirrors build_plugin_2601_vs2026.py + the Linux path.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tools/legacy/build_plugin_zstd_vs2026.py

@@ -631,6 +631,8 @@ Examples:
     parser.add_argument('--vs-version', choices=['auto', '2026', '2022'], default='auto',
                         help='Visual Studio version to use (default: auto)')
 
+    parser.add_argument('--dist', action='store_true',
+                        help='Copy built DLLs to <repo>/dist/<config> instead of <repo>/plugins/<config>')
     args = parser.parse_args()
 
     # Find MSBuild
@@ -642,6 +644,9 @@ Examples:
 
     # Get project paths
     project_dir, project_file, plugins_dir = get_project_paths(platform_toolset)
+    # --dist: redirect output root from <repo>/plugins to <repo>/dist.
+    if args.dist:
+        plugins_dir = plugins_dir.parent / 'dist'
 
     if args.list_project:
         if not project_file.exists():