cpp: Drop experimental query id prefix and change note

Address maintainer review: remove local harness gitignore entry, delete experimental change-note, set @id cpp/mmio-unsanitized-memcpy, drop @security-severity.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Tito0015

.gitignore

@@ -79,6 +79,3 @@ node_modules/
 
 # Mergetool files
 *.orig
-
-# Local CodeQL harness database cache (veraptos TP/TN validation)
-codeql_harness_dbs/

cpp/ql/src/change-notes/2026-08-31-mmio-unsanitized-memcpy.md

@@ -4,9 +4,8 @@
  *              macros without bounds validation may overflow destination buffers.
  * @kind path-problem
  * @problem.severity error
- * @security-severity 8.6
  * @precision low
- * @id cpp/experimental/mmio-unsanitized-memcpy
+ * @id cpp/mmio-unsanitized-memcpy
  * @tags security
  *       experimental
  *       external/cwe/cwe-120