Point US manifest to core 3.26.1-compatible release

[MaxGhenis]

Summary

• points the bundled US data release manifest at the HF commit that certifies policyengine-core 3.26.1 compatibility
• regenerates the US TRACE TRO for the new immutable manifest URL
• updates manifest tests to preserve built-with core 3.26.0 while recognizing runtime compatibility with 3.26.1

Tests

• python3 -m json.tool src/policyengine/data/release_manifests/us.json >/dev/null
• uv run python -m pytest tests/test_release_manifests.py tests/test_trace_tro.py tests/test_bundle_refresh.py
• uv run ruff format --check tests/test_release_manifests.py
• uv run ruff check tests/test_release_manifests.py