docs: Add comprehensive ACP Constitution (#256)

## Summary

- Add constitution template to project documentation
- Expand constitution from template to comprehensive governance document
- Establish 10 core principles for the Ambient Code Platform

## Changes

### Constitution Document (.specify/memory/constitution.md)
Transformed from placeholder template to comprehensive 360+ line
governance document:

**Core Principles** (10 total):
1. **Kubernetes-Native Architecture** - CRDs, Operators, Jobs, RBAC
2. **Security & Multi-Tenancy First** - Authentication, authorization,
token security
3. **Type Safety & Error Handling** - No panic, explicit errors,
type-safe unstructured access
4. **Test-Driven Development** - Contract, integration, unit,
permission, E2E tests
5. **Component Modularity** - Single-responsibility modules, no cyclic
dependencies
6. **Observability & Monitoring** - Structured logging, health/metrics
endpoints
7. **Resource Lifecycle Management** - OwnerReferences, idempotency,
cleanup
8. **Context Engineering & Prompt Optimization** - Token budgets, prompt
templates
9. **Data Access & Knowledge Augmentation** - RAG, MCP, RLHF
10. **Commit Discipline & Code Review** - Line count thresholds, atomic
commits, conventional format

**Development Standards**:
- Go code guidelines (formatting, error handling, K8s client patterns)
- Frontend guidelines (Shadcn UI, React Query, type safety)
- Python guidelines (virtual environments, uv, black/isort)

**Deployment & Operations**:
- Pre-deployment validation commands
- Production security, monitoring, scaling requirements

**Governance**:
- Amendment process with semantic versioning
- Compliance requirements and development guidance

### Documentation (docs/reference/constitution.md)
Added reference documentation with link to constitution source

### MkDocs Configuration (mkdocs.yml)
Added constitution to reference section of documentation site

## Test plan

- [x] Markdown linting passes (line length warnings ignored per project
standards)
- [ ] Verify documentation renders correctly on MkDocs site
- [ ] Review all 10 principles for clarity and applicability
- [ ] Validate development standards match current project practices
- [ ] Confirm governance process is practical and enforceable

## Follow-up TODOs

As noted in constitution changelog:
- Implement /metrics endpoints in all components
- Create prompt template library
- Design RAG pipeline architecture
- Add commit size validation tooling (pre-commit hook or CI check)
- Update PR template to include commit discipline checklist

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: jeremyeder