feat(workflow-executor): handle orchestrator 409 conflict on aborted runs

[matthv]

Summary

• Add RunConflictError boundary error for orchestrator 409 rejections
• Detect conflict messages in ForestServerWorkflowPort.updateStepExecution() (run aborted, already terminated, or step revised)
• Handle RunConflictError gracefully in the Runner with an info log instead of treating it as a fatal error

When the orchestrator aborts a run while the executor is mid-step, the executor now:

1. Completes the step execution locally (no interruption)
2. Detects the 409 when reporting the outcome
3. Logs an info message and moves on (no retry, no error)

Test plan

• yarn workspace @forestadmin/workflow-executor test — 433 tests pass
• 4 new tests in forest-server-workflow-port.test.ts (conflict detection + re-throw)
• 2 new tests in runner.test.ts (graceful handling vs error logging)

🤖 Generated with Claude Code

Note

Handle orchestrator 409 conflict errors on aborted runs in workflow executor

• Adds a new RunConflictError class in errors.ts to represent cases where a run can no longer be updated (aborted, finished, or revised).
• updateStepExecution in forest-server-workflow-port.ts now catches POST errors and throws RunConflictError when the server response contains 'cannot be updated', 'already terminated', or 'revised'.
• The runner treats RunConflictError as a non-failure condition, logging an info message instead of an error when step outcome reporting hits a conflict.

^{Macroscope summarized 467fddf.}