v1.3.0 — environment diagnostics (--env), implements the dsh doctor idea (#1719)
New --env command implementing discussion #1719: node version, pnpm availability, dsh on PATH, and Web UI port 3080 availability.
- 12 unit tests (2 new env tests), packaged plugin-shell smoke, full self-check all pass
- Also includes v1.2.0's profile host-shadowing tripwire
- README EN/ZH updated