chore: pre-launch cleanup and enterprise section

[bordeauxred]

Summary

Pre-launch cleanup and developer experience improvements for going public.

Cleanup:

• Remove unimplemented tau2 adapter stub and all references (cli, pyproject, comments)
• Remove CAR_BENCH_TESTED_COMMIT = "TBD" placeholder from CARAdapter
• Gitignore playbook.json and runs/ (runtime artifacts)

Enterprise & metadata:

• Add Enterprise section to README (advanced evolution, persistent playbooks, managed training, logging & lineage)
• Add Website and Documentation URLs to pyproject.toml
• Set repo homepage to aganthos.com

Developer experience:

• Add MkDocs documentation site with GitHub Pages deployment (concepts, getting started, adding environments)
• Expand CONTRIBUTING.md with architecture overview, testing guide, code style, adapter guide
• Add GitHub issue templates (bug report, feature request) and PR template

Test plan

• 958 tests pass, 0 failures
• Codex code review: no issues flagged
• Gemini code review: runs/ gitignore suggestion addressed
• CI passes on this PR
• Verify README renders correctly on GitHub

Co-authored-by: Claude Opus 4.6 noreply@anthropic.com

[gemini-code-assist]

Code Review

This pull request performs a pre-launch cleanup by removing the unimplemented tau2 adapter and its associated stubs from the CLI, core logic, and project configuration. It also updates the README with an Enterprise section, adds a website link to the project metadata, and includes playbook.json in the .gitignore. Feedback suggests also adding the runs/ directory to .gitignore to prevent local execution logs from being accidentally committed.

[gemini-code-assist]

Since this PR focuses on pre-launch cleanup and explicitly adds playbook.json as a runtime artifact to .gitignore, it is highly recommended to also include the runs/ directory. The ExperimentLog and EvolutionLog classes default to creating this directory for storing execution traces and logs (e.g., ./runs/<bench>/<timestamp>). Ignoring it prevents local run data from being accidentally committed to the repository.

# Runtime artifacts
playbook.json
runs/