[host-numerics] 1/N: basic scaffolding of new shared component

[newling]

This is PR 1/N in a sequence introducing a shared host-numerics component.

The complete working prototype is available in draft PR #10553. That PR currently contains the end-to-end result and will remain open as a reference and integration test while its implementation is moved into develop through small, independently reviewable changes.

The planned work has four broad phases:

1. Establish the component's build, packaging, Python, testing, and CI foundations, beginning with this PR.
2. Introduce the core tensor and scalar model, together with independent C++ and Python tests.
3. Add the remaining numerical operations, generation facilities, comparison support, and complete standalone testing.
4. Integrate host-numerics into its consumers incrementally, including hipBLASLt, TensileLite, and rocRoller, while removing the implementations it replaces.

The first three phases deliberately do not change any consumer. This keeps development isolated from hipBLASLt, TensileLite, and rocRoller behavior and allows each change to use a small, CPU-only GitHub Actions job. The target is for the component build and tests themselves to complete in under two minutes, excluding runner queue and provisioning time.

The endpoint demonstrated by #10553 is a large refactor of host-side data generation and numerical validation (+51,927 / -63,657 at the start of this series). It creates a standalone CPU-only shared component used by hipBLASLt, TensileLite, and rocRoller. It absorbs the reusable responsibilities currently provided by mxDataGenerator, allowing that package to be removed after its consumers migrate.

This first PR intentionally contains almost no numerical functionality. It establishes the roc::host-numerics-core and roc::host-numerics CMake targets, an installable ROCHostNumerics CMake package, an importable roc_host_numerics Python module, C++/Python/package smoke tests, a dedicated CPU-only GitHub Actions workflow, and initial ownership.

Nothing in this PR is connected to an existing product or added to the default monorepo build.

Testing

Built and tested the standalone component with Clang and GCC. Verified the C++ target, Python import, installation, and an external find_package(ROCHostNumerics) consumer. Repository pre-commit checks pass.

[therock-pr-bot]

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⛔ Forbidden Files	✅ Pass	—
🧪 Unit Test	✅ Pass	—
🔎 pre-commit	✅ Pass	—
🚫 Draft PR	🔜 To Be Enabled	—
🚩 Feature Flag	🔜 To Be Enabled	—
📊 Code Coverage	🔜 To Be Enabled	—
🤖 therock-pr-bot	✅ Pass	—

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[therock-pr-bot]

🎉 All checks passed! This PR is ready for review.