Bump nx to 0.11 (override Bumblebee's upstream constraint)

[ausimian]

Summary

• Bump nx from 0.10 → 0.11. Bumblebee's pinned main commit (which is also the current upstream HEAD) still declares nx ~> 0.9.0 or ~> 0.10.0, so override: true on our requirement is what actually unlocks 0.11. Bumblebee's source is compatible with 0.11 — the full test matrix runs green.
• Noted the override in RELEASE.md under ## Changed with a reminder to drop it once Bumblebee publishes past nx 0.10.
• axon 0.8 and scidata 0.1.11 deliberately left alone — axon is blocked by the same Bumblebee constraint, and scidata's newer versions tighten castore ~> 0.1 which conflicts with tokenizers' castore 1.x.

Test plan

• mix precommit — 425 tests, 0 failures
• mix test --include conformance --include qwen3_full --include qwen3_quant_full --include vit_full --include whisper_full --include distilbert_full --include training_full --include fast_kernels_full — 453 tests, 0 failures (tiny-random + full-size Qwen3, ViT, Whisper, DistilBERT; fused kernels; MNIST training; quantised Qwen3)
• mix compile --warnings-as-errors under MIX_ENV=test — clean

[ausimian]

Abandoning — keeping emily's nx constraint at ~> 0.10 is fine; consumers can pin nx 0.11.x themselves, and this branch verified that works.