Release AIKernel.Demo v0.1.2 examples workspace (#2)

## Summary
This PR releases AIKernel.Demo v0.1.2 as the official examples workspace for AIKernel.

## Changes
- Aligns Demo projects with official AIKernel 0.1.2 NuGet packages.
- Removes local package feed dependency from the demo repository.
- Updates demo guidance and educational comments.
- Keeps Demo as runnable examples rather than a publishable package family.

## Validation
- dotnet restore
- dotnet build
- dotnet test

## Release
This PR prepares AIKernel.Demo v0.1.2 for GitHub release as the official examples workspace.

Release 0.1.1: Verify the Semantic OS end-to-end (#1)

## Summary
- Finalizes the 0.1.1 demo system across the official AIKernel layers.
- Adds Python release-surface parity for the C# golden-path demos.
- Updates demo documentation so users can understand the Semantic OS structure from practical examples.

## Validation
- Release build passed.
- Demo test suite passed.
- Python demo tests passed.