dev --logs on harness-only project exits 0 instead of failing

[Hweinstock]

agentcore dev --logs on a harness-only project prints guidance text and exits 0. It should exit 1 with a
validation error since no dev server can be started, harness projects don't support local dev.

Reproduction:

 agentcore create --name MyHarness
 cd MyHarness
 agentcore dev --logs --skip-deploy
 # Prints "Harness dev runs against the deployed service..." and exits 0

Expected: Exit code 1 with a clear error (e.g. "Harness projects do not support local dev. Use agentcore
invoke --harness instead.")

Actual: Exit code 0 with informational text.