Empty phases now complete as $0 drafts instead of failing

Generating an estimate before adding scope now completes as a draft instead of failing.

Bug Fixes

Fixed a regression where generating an estimate on a phase with no scope entries would fail with a pipeline error. Estimates now complete as $0 drafts, allowing teams to explore scope and build estimates incrementally. This fix is particularly important for phases without deterministic job-level rules (like remediation-abatement).