Add C++ regex parser and RegexTreeView (Phase 1)

Author: Copilot

cpp/ql/lib/change-notes/2026-07-15-cpp-regex-tree-view.md

@@ -0,0 +1,4 @@
+---
+category: newQuery
+---
+* Added an internal C++ regular-expression parse library (`semmle.code.cpp.regex.RegexTreeView`) that implements the shared `RegexTreeViewSig` signature. This is the foundation for future ReDoS analyses for C++ (`cpp/polynomial-redos` and `cpp/redos`). No new queries are added in this release.

cpp/ql/lib/qlpack.yml

@@ -10,6 +10,7 @@ dependencies:
   codeql/mad: ${workspace}
   codeql/quantum: ${workspace}
   codeql/rangeanalysis: ${workspace}
+  codeql/regex: ${workspace}
   codeql/ssa: ${workspace}
   codeql/typeflow: ${workspace}
   codeql/tutorial: ${workspace}