## Context
Fixes#22947.
A workflow with If/Else branches could fail at runtime with `Step not
found` (and no detail in the Runs panel) because of dangling
`nextStepIds` in the workflow graph — references to steps that no longer
exist.
## Root cause
An If/Else routes only through `settings.input.branches[].nextStepIds`;
its top-level `nextStepIds` is never read by the executor and must stay
empty. But converting an existing step into an If/Else copied the
previous step's `nextStepIds` onto the new If/Else, leaving a stray
top-level reference. That reference is invisible to the executor, and
when steps around it are later deleted it becomes dangling and
propagates into a normal step's `nextStepIds`, which the executor then
tries to follow — `Step not found`.
## Fix
When a step's type is changed to If/Else, don't carry over the previous
step's `nextStepIds`. One change in
`workflow-version-step-update.workspace-service.ts`.
## Verification
Reproduced on a local instance via the editor's GraphQL mutations (build
`trigger → P → X → D`, convert X to If/Else, delete D then X):
- Before: converting X produced a stray `nextStepIds: [D]`, and after
the deletes P was left with a dangling reference.
- After: converting X yields `nextStepIds: []`, and P stays clean — no
dangling reference.
Thomas Trompette
9e2c870574