CI/Dev env bump (#1818)

### What does this PR do?

Type of change: chore

Bumps CI/dev tooling and test containers.

**Container bumps**
- NeMo test containers → 26.06
- TRT-LLM container → 1.3.0rc19
- transformers max version → 5.12

**Dev tooling bumps**
- ruff bump 0.12.11 → 0.15.18
- mypy 1.17.1 → 2.1.0: enable new defaults (`local_partial_types`,
`strict_bytes`); fix/narrow the errors newly surfaced by mypy 2.0 in 4
modules (rather than blanket-suppressing them); remove 2 stale `# type:
ignore` comments
- pre-commit 4.3.0 → 4.6.0
- sphinx 8.1 → 9.1 + sphinx-rtd-theme 3.0 → 3.1: add `suppress_warnings
= ["ref.python"]` to fix cross-reference ambiguity error new in sphinx
9.x
- trl fix for newly released 1.7 version

**Bug fixes surfaced by the bumps**
- sparsity (weight): make the weight mask DTensor-aware under FSDP. The
transformers→5.12 bump routes the HF Trainer FSDP optimizer-state save
through torch's DTensor-based `get_optimizer_state_dict`, which
triggered `aten.mul.Tensor got mixed torch.Tensor and DTensor` in the
dynamic `weight` getter. The mask is now distributed to the weight's
mesh/placements before masking, cached, and rebuilt only when the
sharding changes (invalidated on `set_mask`). Fixes the `llm_sparsity`
example test.

### Testing

- `pre-commit run --all-files` ✅ (including mypy 2.1.0)
- `nox -s docs` ✅
- `tests/unit/torch/sparsity` + `tests/unit/torch/nas` ✅
- `llm_sparsity` GPU example test (FSDP path) verified in CI

### Before your PR is "*Ready for review*"

- Is this change backward compatible?: ✅
- If you copied code from any other sources or added a new PIP
dependency, did you follow guidance in `CONTRIBUTING.md`: N/A
- Did you write any new necessary tests?: N/A
- Did you update
[Changelog](https://github.com/NVIDIA/Model-Optimizer/blob/main/CHANGELOG.rst)?:
N/A
- Did you get Claude approval on this PR?: ✅
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

## Summary

* **Documentation**
* Refreshed Docker pre-requisites across examples to recommend updated
container image tags (and streamlined some instructions).
* **Bug Fixes**
* Improved sparse weight mask handling for DTensor/FSDP by aligning and
caching distributed masks.
  * Made TensorRT engine byte retrieval return immutable `bytes`.
* Reduced Sphinx cross-reference warnings and tuned Transformers
compatibility warning thresholds.
* **Tests**
  * Increased default unit test timeout on Windows runners.
* **Chores**
* Updated CI workflow container tags and refreshed linting/typing/docs
version pins, plus related mypy configuration.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Keval Morabia <28916987+kevalmorabia97@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/codecov.yml

@@ -9,5 +9,5 @@ coverage:
     project:
       default:
         target: auto
-        threshold: 1% # Allow atmost 1% coverage drop from main branch.
+        threshold: 2% # Allow atmost 2% coverage drop from main branch.
     patch: false

.github/workflows/example_tests.yml

@@ -59,7 +59,7 @@ jobs:
     uses: ./.github/workflows/_example_tests_runner.yml
     secrets: inherit
     with:
-      docker_image: "nvcr.io/nvidia/tensorrt-llm/release:1.3.0rc17"
+      docker_image: "nvcr.io/nvidia/tensorrt-llm/release:1.3.0rc19"
       example: ${{ matrix.example }}
       pip_install_extras: "[hf,dev-test]"
       runner: linux-amd64-gpu-rtxpro6000-latest-1
@@ -73,7 +73,7 @@ jobs:
     uses: ./.github/workflows/_example_tests_runner.yml
     secrets: inherit
     with:
-      docker_image: "nvcr.io/nvidia/tensorrt-llm/release:1.3.0rc17"
+      docker_image: "nvcr.io/nvidia/tensorrt-llm/release:1.3.0rc19"
       example: ${{ matrix.example }}
       pip_install_extras: "[hf,dev-test]"
       runner: linux-amd64-gpu-rtxpro6000-latest-2
@@ -85,7 +85,7 @@ jobs:
     uses: ./.github/workflows/_example_tests_runner.yml
     secrets: inherit
     with:
-      docker_image: "nvcr.io/nvidia/nemo:26.04"
+      docker_image: "nvcr.io/nvidia/nemo:26.06"
       example: megatron_bridge
       timeout_minutes: 45
       pip_install_extras: "[hf,puzzletron,dev-test]"

.github/workflows/gpu_tests.yml

@@ -43,10 +43,10 @@ jobs:
             container_image: nvcr.io/nvidia/pytorch:26.05-py3
           - example: gpu_megatron
             timeout: 60
-            container_image: nvcr.io/nvidia/nemo:26.04
+            container_image: nvcr.io/nvidia/nemo:26.06
           - example: gpu_trtllm
             timeout: 15
-            container_image: nvcr.io/nvidia/tensorrt-llm/release:1.3.0rc17
+            container_image: nvcr.io/nvidia/tensorrt-llm/release:1.3.0rc19
           - example: gpu_vllm
             timeout: 15
             container_image: docker.io/vllm/vllm-openai:v0.20.0