docs: position baloney-detection-kit within the Microsoft agent-governance ecosystem

Add explicit references to Microsoft's official open-source agent tools —
Agent Governance Toolkit (runtime action governance) and ASSERT (spec-driven
evaluation) — alongside the sibling robopsychology, so visitors understand
where each tool plays in the agent lifecycle and how the four compose rather
than compete.

- README.md: new "Where this fits: the agent-governance ecosystem" section
  with a layer/where-to-use table and BDK composition points.
- related-work.md: add ASSERT and AGT rows to the adjacent-tools table, a new
  "Microsoft agent-governance tools (2026)" subsection, and extra columns in
  the positioning summary.
- deployment-contexts.md: new "Pattern 6 - Enterprise agent stack" and a
  decision-summary row.

Integration claims are framed as conceptual composition patterns, not shipped
adapters; prompts-are-advisory and human-in-the-loop boundaries kept explicit.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>