bitdynamics-ab/canton-devkit: docs/e2e-testing.md

# End-to-End Testing Unit tests (`go test ./...`) cover DevKit's Go logic. End-to-end (E2E) tests cover the parts that only a *real* invocation exercises: the DPM component surface, shelling out to `dpm`/`daml`, Docker-backed LocalNet lifecycle, and the artifacts DevKit produces on disk. The reposit