Review Newton Changes

Read REVIEW_GUIDELINES.rst and CODING_GUIDELINES.rst in full. Treat the former as the explicit definitions of the Fit, Requirements, and Standards axes, and enforce the latter during Standards review.

1. Resolve the exact merge base and head. Read the complete merge-base..head diff and commit list.
2. Read the pull-request description, linked issue or specification, relevant primary sources, and CODING_GUIDELINES.rst. If no separate specification exists, use the pull-request description as the stated intent. Do not read existing review comments yet.
3. Perform an adversarial correctness-first Requirements pass. Trace changed inputs, state, counts, offsets, ownership, and outputs through every relevant supported execution mode. Check applicable zero/one/many and capacity boundaries, heterogeneous inputs, toggle/reset/reuse and partial failures, CPU/CUDA and backend differences, autodiff, determinism, graph capture, and numerical invariants. For performance changes, examine setup and steady-state complexity, allocations, synchronization, transfers, and whether benchmarks exercise the changed path. Run a minimal adversarial probe when feasible.
4. Freeze candidate findings before reading existing reviews. Record the location, triggering input or condition, mechanism, observable impact, evidence, and confidence for each candidate.
5. Read the top-level discussion and review threads. Refine or deduplicate the independently discovered concerns; acknowledge existing concerns when they affect the verdict.
6. Review Fit and Standards independently using their definitions in REVIEW_GUIDELINES.rst. When independent agent contexts are available, use separate passes so one conclusion does not bias another.
7. Report Fit and architectural concerns first, but retain every supported material behavioral, correctness, compatibility, and performance finding even when Fit fails. Do not let missing tests, documentation, or measurements replace the search for an underlying behavioral defect.
8. For each remaining concern, state its priority, location, problem, impact, and evidence. Distinguish demonstrated defects from questions, evidence requests, requirements, and judgment calls. Do not prescribe a correction unless the user asks for one.

Aggregate the three axes without suppressing a finding merely because another axis passes. Give the explicit Fit verdict defined by the review guide.