This change improves the isolation of example projects by introducing dedicated
workspace directories. Previously, some examples operated directly within the
SDK repository, which could lead to accidental file changes or git clutter.

Key changes:
- Added workspace directories to .gitignore for all examples.
- Created setup.sh and cleanup.sh for the simple example to manage a local git
  workspace instead of the root repo.
- Introduced standalone run_prompts.exs scripts in example directories using
  Mix.install to simplify execution.
- Updated example prompts and READMEs to reference the local workspace rather
  than the project root.
- Adjusted runner_config.exs in the simple example to target the newly
  created workspace directory.
- Removed legacy output files from the simple example directory.
- Updated the multi-repo dummy example with standalone execution support and
  improved documentation.

These improvements make the examples safer to run and easier to understand as
self-contained units.