refactor: complete bootstrap of ARNES agent harness framework

- Add complete agent harness structure with 8 roles (leader, triager, architect, implementer, reviewer, security, qa, documenter)
- Implement strict workflow with 9 stages and mandatory gates
- Add comprehensive verification script and runtime status tracking
- Create artifact-based evidence system with contracts and schemas
- Add agent policy matrix with permissions and anti-cheat rules
- Include test suite (44 tests passing) and CI-ready structure
- Add documentation: README, HOWTO, CHECKPOINTS, templates
- Configure model routing policies and token-aware task assignment
- Add BDD/SDD specification guides and feature templates
- Include starter pack for quick project onboarding

All verification checks pass. Framework ready for production use.

harness/policies/model-routing.md

@@ -0,0 +1,24 @@
+# Policy: Model routing
+
+Use model by task complexity, not by habit.
+
+## Core rule
+- Start small.
+- Escalate only when blocked or quality poor.
+
+## Escalation triggers
+- Repeated failed attempts.
+- Ambiguous requirements.
+- Cross-module side effects.
+- Security-critical code paths.
+
+## De-escalation triggers
+- Routine CRUD edits.
+- Mechanical refactors.
+- Artifact writing.
+- Status/timeline updates.
+
+## Required behavior
+- Record chosen model class in artifact header when work is non-trivial.
+- Keep outputs concise to reduce token burn.
+- If `harness/project.config.json` has `model_mode=lean`, prefer tiny/small whenever possible.