Add demo project for Personal Tracker MVP-1

Create example project structure in examples/demo-project/ with:
- Project metadata in meta/project.yaml
- README, LOG, CHANGELOG and TASKS documentation
- Two detailed session files showing real work examples
- Empty docs/ and assets/ directories

The demo project serves as a reference implementation showing
how to use the Personal Tracker CLI effectively.

examples/demo-project/meta/project.yaml

@@ -0,0 +1,13 @@
+id: demo-001
+name: Demo Project
+slug: demo-project
+description: Proyecto de demostración del tracker personal
+type: misc
+status: active
+tags:
+  - demo
+  - example
+repo_path: null
+created_at: "2026-03-20T10:00:00"
+updated_at: "2026-03-23T12:00:00"
+last_session_at: "2026-03-22T14:30:00"