fix(gasoline): bound workflow loop traces

[Dheerajvarma1]

Summary

Fixes #5671.

Gasoline workflow iterations previously inherited the long-lived LoopBuilder::run tracing span, causing every iteration to remain in the same OpenTelemetry trace.

This change:

• creates a new root trace for each workflow iteration
• links the iteration span back to the long-lived workflow span
• preserves the existing iteration execution behavior

Verification

• cargo fmt --check ✅
• cargo check -p gasoline ✅
• git diff --check ✅

cargo test -p gasoline currently fails during compilation of two existing integration tests unrelated to this change:

• engine/packages/gasoline/tests/db_bump.rs
• engine/packages/gasoline/tests/workflows/tags_test.rs

The modified file is engine/packages/gasoline/src/builder/workflow/lupe.rs.