v1.5.0 — preflight mode (activation preflight from discussion #1774)
New preflight alias: dsh-plugin-doctor preflight ./my-plugin runs build + pack + fresh-profile install + composed-config verification — matching the 'activation preflight' proposal in discussion #1774.
- 12 unit tests, packaged plugin-shell smoke, preflight self-check all pass
- README EN/ZH updated