docs: add HANDOVER_KNOWLEDGE_BASE.md for maintainer onboarding

[busehalis-sap]

Summary

• Adds HANDOVER_KNOWLEDGE_BASE.md as onboarding material for the next maintainer
• Covers plugin architecture, runtime mode detection, and the two notification emit paths (programmatic and declarative)
• Documents 8 key architectural decisions (ADRs) with context and rationale
• Includes module-level walkthrough of all major classes with non-obvious implementation details
• Covers testing strategy, hybrid testing setup, DB storage/cooldown, and how to extend the plugin with new ANS endpoints

Intended audience

Incoming maintainer with CAP Java background — no prior knowledge of this plugin assumed.

[hyperspace-pr-bot]

👋 Hi — I'm PR Bot, your SAP code review assistant.

I'll automatically review your pull requests for code quality, security, and SAP compliance. Get an overview of what I do →

What I do

• Summarize your pull request changes
• Review code for quality, correctness, and reliability
• Suggest fixes when a pipeline job fails

Key commands

Command	Description
/review [--all]	Trigger a code review. Add --all to include files excluded by excluded_paths.
/summarize	Generate a PR summary
/ask <question>	Ask about the current changes
/help	See all available commands

Configure me for your team

Create .hyperspace/pull_request_bot.json in your repository:

{
  "$schema": "https://devops-insights-pr-bot.cfapps.eu10-004.hana.ondemand.com/schema/pull_request_bot.json",
  "features": {
    "control_panel": false,
    "summarize": {
      "auto_generate_summary": true,
      "auto_insert_summary": true,
      "auto_run_on_draft_pr": true,
      "use_custom_summarize_prompt": false,
      "use_custom_summarize_output_template": false,
      "excluded_paths": [],
      "auto_exclude_authors": []
    },
    "review": {
      "auto_generate_review": true,
      "auto_run_on_draft_pr": false,
      "use_custom_review_focus": false,
      "excluded_paths": [],
      "auto_exclude_authors": []
    },
    "sonar_fix": {
      "enable": true,
      "excluded_rules": []
    },
    "pipeline_fix": {
      "enable": true
    }
  },
  "excluded_paths": []
}

Full configuration reference →

*This introduction message will be shown to you only once, you will not see it in future PRs.

[lisajulia]

One small change, otherwise this is fine :) Thanks!