Normalize swift-tools-version to 6.3.3 (fleet ruling 2026-07-10)

One manifest per package, pure 6.3.3 line. Fleet compile gate: the
395-member institute-ALL workspace build passed post-bump.

Claude-Session: https://claude.ai/code/session_01BYnNsRb9tr41cy36oWDFLU

Author: coenttb

.github/repro/cross-package/base/Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 6.1
+// swift-tools-version: 6.3.3
 // Base package for the cross-package debug-info-mangler repro.
 // Provides the spec namespace root + the load-bearing namespace TYPEALIAS
 // (mirrors swift-pdf-standard's `public typealias PDF = ISO_32000`).

.github/repro/cross-package/crash/Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 6.1
+// swift-tools-version: 6.3.3
 // Crash package for the cross-package debug-info-mangler repro.
 // Extends the OTHER package's typealias-sugared namespace with nested
 // protocols and forms their existentials at a debug-info-emitting site

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 6.3.1
+// swift-tools-version: 6.3.3
 
 import PackageDescription