refactor: reorganize examples directory with topic-based subdirectories

Reorganize examples directory into logical topic-based subdirectories with
comprehensive documentation:

- templates/: ISO/ARC42 documentation templates
- asset-management/: Asset management prototypes and demos
- essays/: Long-form content examples
- invoicing/: Invoice generation examples
- plugins/: Plugin development examples
- issue-demos/: Issue prevention demonstrations
- design-patterns/: Design pattern examples

Each subdirectory includes a README.txt file with topic description and
contributor signatures based on file creation timestamps.

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

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

examples/asset-management/README.txt

@@ -0,0 +1,14 @@
+Asset Management Examples
+
+This directory contains prototype implementations and demonstrations for asset management
+concepts developed for Issue #141:
+
+- asset_management_concept_a.py: Hash-based content-addressable storage approach
+- asset_management_concept_b.py: Alternative asset management implementation
+- demo_hash_store/: Working demonstration of hash-based asset storage with metadata
+- demo_workspace/: Example workspace showing asset management in practice
+
+These examples showcase different approaches to asset deduplication, storage, and
+management within the MarkiTect ecosystem.
+
+--worsch, 25-10-08