refactor(test): decouple examples from test infrastructure

[moonyue-w]

Summary

• move shared live/offline test support from examples/testutil into internal/testsupport
• repoint Forward and Managed tests to the internal test-support package
• keep examples independent from tests and preserve the full runnable topic set
• create the Forward execution-E2E Identity with a name so mounted memory is materialized

Validation

• make lint
• make build
• make test
• make docs-check
• CN live: skill_and_memory focused E2E passed after the Identity-name fix