[EMPLOYEE] Implement Technical Writer Agent

Implement the H2A2H **Technical Writer Agent** from `employees/product-design/technical-writer/`. Canonical identity: `Enterprise.Employee.TechnicalWriterAgent` ## Required implementation - [ ] Load and validate `agent-card.json` as the initial A2A discovery identity. - [ ] Load `h2a2h.employee.yml` as the role/authority contract. - [ ] Bind every declared Intent to an implementation without hidden role configuration. - [ ] Implement only the declared tool allowlist and enforce tool permissions. - [ ] Validate OpenDelegation before every side effect. - [ ] Resolve transports/channels from OpenEntityChannels/OpenIntent, not ad hoc role code. - [ ] Preserve `correlation_id`, causation, provenance and responsibility chain. - [ ] Enforce Human approval triggers and fail closed outside delegated scope. - [ ] Produce Proof-of-Human-Return for Human-boundary results. - [ ] Add unit, conformance and end-to-end tests for one successful and one denied/escalated scenario. - [ ] Prove interoperability without implementation-specific coupling. ## Definition of Done The Agent can be discovered through its A2A Agent Card, invoked only inside valid H2A2H delegation, use only declared tools, complete role-specific work, preserve auditability/responsibility, and return evidence to the accountable Human.