docs: add badges, hummbl.io link, and expand HUMMBL ecosystem

README.md

@@ -5,11 +5,14 @@
 [![Python 3.11+](https://img.shields.io/badge/python-3.11%2B-blue)](https://www.python.org/downloads/)
 [![License](https://img.shields.io/badge/license-Apache%202.0-blue)](LICENSE)
 [![Dependencies](https://img.shields.io/badge/core_deps-stdlib_only-brightgreen)]()
+[![Last commit](https://img.shields.io/github/last-commit/hummbl-dev/arbiter/main)](https://github.com/hummbl-dev/arbiter/commits/main)
 
 **Agent-aware code quality scoring for multi-agent codebases.**
 
 In 2026, code is written by fleets of AI agents. Arbiter knows *who* wrote each line -- human or AI -- and scores quality accordingly.
 
+Learn more at [hummbl.io](https://hummbl.io).
+
 Repository health, validation, and stewardship expectations are tracked in [docs/REPO_HEALTH.md](docs/REPO_HEALTH.md).
 
 ## Quick Start -- 5 Minutes
@@ -148,6 +151,8 @@ Part of the [HUMMBL](https://github.com/hummbl-dev) cognitive AI architecture:
 
 - [hummbl-governance](https://github.com/hummbl-dev/hummbl-governance) -- Governance primitives that Arbiter scores against
 - [base120](https://github.com/hummbl-dev/base120) -- 120 mental models for structured reasoning
+- [hummbl-agent](https://github.com/hummbl-dev/hummbl-agent) -- Governed control plane for AI agent systems
+- [hummbl-bibliography](https://github.com/hummbl-dev/hummbl-bibliography) -- Bibliography for the HUMMBL cognitive framework
 - [mcp-server](https://github.com/hummbl-dev/mcp-server) -- MCP server for AI agent integration
 
 Learn more at [hummbl.io](https://hummbl.io).