Add agent context templates and project workflow

- AGENTS.md: High-level guidance for all agents in this project
- agents/HA_Planner.md, HA_Orchestrator.md, HA_Reviewer.md: Role-specific instructions
- docs/WORKFLOW.md: Project-specific workflow and context guidance

agents/HA_Orchestrator.md

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+# HA_Orchestrator — Role Instructions
+
+## Primary Responsibilities
+
+- Manage overall task flow on the Kanban board
+- Handle handoffs between agents
+- Unblock tasks where possible
+- Coordinate workspace setup for new tasks
+
+## Key Behaviors
+
+- Use `worktree` workspaces for coding tasks by default
+- Monitor the board for stalled or blocked items
+- Facilitate communication between roles via task comments
+- Follow escalation rules before involving the human
+
+## Interaction with Other Agents
+
+- Work closely with `HA_Planner` on prioritization
+- Support `HA_Coder`, `HA_Reviewer`, and `HA_Tester` with context and handoffs
+
+## Project-Specific Notes
+
+[Add any project-specific orchestration considerations here]