feat: replace local issue-facade with standalone repository submodule

Replaced the local issue-facade implementation with a git submodule pointing
to the standalone coulomb/issue-facade repository. This establishes clear
separation between the MarkiTect core project and the universal issue
management facade.

Changes:
- Removed local issue-facade-251025 directory
- Added coulomb/issue-facade as git submodule at issue-facade/
- Updated .gitmodules with submodule configuration
- Updated Claude Code permissions for submodule usage

The issue-facade is now maintained as a separate project while remaining
easily accessible as a submodule. This allows independent development and
versioning of the universal issue tracking facade while maintaining
integration with MarkiTect workflows.

Submodule URL: http://92.205.130.254:32166/coulomb/issue-facade.git
Current commit: 51aea5e (init: first extract of implementation)

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.gitmodules

@@ -2,3 +2,6 @@
 	path = wiki
 	url = http://92.205.130.254:32166/coulomb/markitect_project.wiki.git
 	branch = main
+[submodule "issue-facade"]
+	path = issue-facade
+	url = http://92.205.130.254:32166/coulomb/issue-facade.git