docs: file R13 (pre-existing serverless ruff B904 debt) as tracked backlog item

docs/BACKLOG_RESOLUTION_2026-06-09.md

@@ -77,6 +77,8 @@ Goal-driven systematic resolution of every pending item. This doc is the live au
 
 **Wave 3 — DONE (Phase-7 reconciliation):** R1 ✅ (HeldOutGuard wired into ComposerReplicationTrainer — optional, OFF by default, soft/hard stop; + integration test), R2 ✅ (HeldoutSplit disjointness enforcer `safety/holdout.py` + 10 tests), R3 ✅ (EKS entrypoint contract bug fixed — `replica_entrypoint.__main__` now resolves from env OR argv; proven end-to-end with a pure-env invocation), R4 ✅ (calibrate_kl_threshold rejects factor<=0/negative-baseline + positive floor), R7 ✅ (API_REFERENCE §15-17: EKS/SageMaker/DockerSandbox/safety), R8 ✅ (ADR-015 authored + indexed), R10 ✅ (path-(c) divergence-rate test). R12 ✅ (B4/B7 complete). R5 ✅ (EKS+SageMaker cancel now re-raise unexpected errors, swallow only 404/409/already-terminal + propagation test), R6 ✅ (EKS collect() result dicts include `result`=rendezvous URI), R11 ✅ (spike-006 test seeded torch.manual_seed(0) → no longer contention-flaky). ALL Wave-3 items (R1-R11) CLOSED.
 
+**Pre-existing tech-debt (discovered, tracked, OUT of this effort's scope — do not silently reformat the existing codebase):** R13 — ~14 `ruff B904` (raise-without-from) + import-order nits in PRE-EXISTING serverless files (executor.py, hf_jobs.py, modal.py, modal_spawn.py, + 4 pre-existing tests) and spike-006 smoke files. These predate Wave 1-3; a `ruff --fix` would touch unauthored code. Filed for a dedicated lint-debt pass. My Wave 1-3 files are all ruff-clean.
+
 Sandbox refactor verdict: **clean** (no regression to LocalSubprocessSandbox/FeatureDeletionEnv).
 
 ## Wave plan