fix(chaining): add WorkflowUpdateEvent for legacy feature flag (#4824)

[EvaE-Filigran]

Proposed changes

• Add @WorkflowUpdateEvent annotation on the legacy REST API callback path (InjectExecutionService.handleInjectExecutionCallback) so that the inject chaining pipeline is notified when execution traces are processed via the legacy route

Testing Instructions

1. Enable LEGACY_INGESTION_EXECUTION_TRACE feature flag (or use main-ff where all flags are active)
2. Create a scenario with chained injects (inject A → condition → inject B)
3. Execute inject A
4. Verify that step receives the structured output from inject A
5. Verify that the condition evaluates and inject B is triggered

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality
• For bug fix -> I implemented a test that covers the bug

Further comments

On main-ff, all feature flags are enabled (FEATURE_FLAG_ALL = "*"), including LEGACY_INGESTION_EXECUTION_TRACE. This forces execution traces to always go through the legacy REST API callback instead of the queue path. The callback was missing @WorkflowUpdateEvent, so the chaining system was never notified of inject completion — steps never received outputs and conditions were never evaluated.

[Copilot]

Pull request overview

This PR aims to restore inject chaining notifications when execution traces are ingested through the legacy REST callback path (triggered by LEGACY_INGESTION_EXECUTION_TRACE), by adding @WorkflowUpdateEvent to InjectExecutionService.handleInjectExecutionCallback.

Changes:

• Add @WorkflowUpdateEvent on the legacy execution-trace callback handler in InjectExecutionService.
• Import WorkflowUpdateEvent into the legacy inject execution service.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.65%. Comparing base (c837567) to head (bb95c94).

❌ Your project check has failed because the head coverage (2.94%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6499      +/-   ##
============================================
- Coverage     44.67%   44.65%   -0.03%     
- Complexity     7619     7622       +3     
============================================
  Files          2321     2321              
  Lines         64607    64614       +7     
  Branches       8574     8575       +1     
============================================
- Hits          28864    28852      -12     
- Misses        33911    33931      +20     
+ Partials       1832     1831       -1     

Flag	Coverage Δ
backend	66.97% <100.00%> (+<0.01%)	⬆️
e2e	18.36% <ø> (-0.69%)	⬇️
frontend	2.94% <ø> (ø)

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[savacano28]

Tests for FF in chaining: OK

• All : openaev.enabled-dev-features=* => OK

• Only chaining: openaev.enabled-dev-features=INJECT_CHAINING => OK

• No chaining:
  Atomic: OK

Simualtion time based:

[impolitepanda]

Re approved after fixes from tests