Builder launch loop: clean-exit relaunch should rerun the harness fresh (no --resume), matching architect semantics from #1264

[waleedkadous]

Follow-up to #1264, which fixes clean-exit-rerun-fresh semantics for architect terminals (SessionManager-managed restartOnExit).

Builder terminals are out of #1264's scope but have two related gaps:

1. Their while true bash launch loop bakes --resume <id> into the single command it reruns — so the Enter-gated relaunch after a clean exit resumes the conversation the user just ended, violating the Regression (3.2.4): double Ctrl-C on an agent no longer restarts it fresh — classified as deliberate quit #1264 spec (clean exit → fresh rerun, no recovery). A fix needs the generated script to carry a second, fresh-args fragment for the clean-exit branch.
2. Whether builders should keep the Enter gate (added by [Bugfix #1241] Auto-restart only on unnatural exits — a deliberate quit ends cleanly #1244) or auto-rerun like architects is an open product question — builders are porch-driven, and a fresh conversation's interaction with the porch prompt/task state needs thinking through before auto-rerun is safe.

Deliberately deferred from #1264 (bugfix scope, architect-only). Design discussion welcome before spawning.