Audit docs/tutorials for accuracy after demo removal and recent Sherpa changes

[amirfz]

Context

Raised in review on #562 (removed all demos except software_modeler and blueprint_parser_creator).

@20001LastOrder flagged that the docs/tutorials may be out of date, independent of the demo removal:

• docs/How_To/Tutorials/search_refinement.rst still references cd demo/pdf_question_answering, a demo that no longer exists after Remove all demos except software_modeler and blueprint_parser_creator #562.
• docs/How_To/Tutorials/multi_agent.rst contains a snippet (agent1_runtime.proxy().wait()) that may not reflect the current Sherpa API.

Ask

Do a pass over docs/How_To/Tutorials/ to:

• Remove/update references to deleted demos (blog_writer, pdf_question_answering, question_answering, state_based_question_answering, multi-agents, github_linear_mcp_integration)
• Verify code snippets still match current Sherpa APIs
• Fix or remove tutorials that can no longer be followed end-to-end

Good candidate task for a student contributor.