docs: design executable sys mock tools

docs/superpowers/specs/2026-08-13-dap-was-sys-executable-mock-tools-design.md

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+# dap-was-sys Executable Mock Tools Design
+
+## Scope
+
+Implement `sys_system_status` and `sys_notice_list` as executable, read-only MCP tools and REST endpoints in `dap-was-sys`.
+
+## Architecture
+
+Each tool has a request DTO, response DTO, `@McpTool` UseCase interface, and Spring `@Service` implementation. The implementation returns deterministic synthetic data without external calls. A REST controller delegates to the same UseCases, so MCP and HTTP return the same DTO contracts.
+
+## Contracts
+
+- `sys_system_status`: optional `environment`; returns `systemName`, `environment`, `status`, and `checkedAt`.
+- `sys_notice_list`: optional `category`; returns a list of notices with `title`, `priority`, and `publishedDate`.
+- REST endpoints: `GET /api/sys/status` and `GET /api/sys/notices` with their matching optional query parameters.
+
+## Safety
+
+Both tools remain read-only, non-destructive, and idempotent. All data is synthetic; no credentials, personal data, or external integrations are used.
+
+## Validation
+
+Unit tests will verify each UseCase response. MockMvc tests will verify endpoint success, optional parameter handling, and the exposed response fields. Existing YAML definitions and JSON mock responses remain aligned with the DTO contracts.