Bazel C/C++ Toolchains for S-CORE release v1.0

## Summary
Prepare and publish `score_bazel_cpp_toolchains` for the S-CORE `v1.0` release.

This issue tracks the release readiness work for the Bazel C/C++ toolchain configuration repository used by S-CORE. The repository provides Bazel module extension logic, package metadata, templates, and validation examples for Linux and QNX toolchains. It does not ship compiler binaries directly.

## Goal
Deliver a release-ready `bazel_cpp_toolchains` version aligned with the S-CORE `v1.0` release, including validated toolchain definitions, updated documentation, and reproducible package metadata.

## Scope
The release should cover:
TBD

## Proposed Deliverables
- Release tag/version for `bazel_cpp_toolchains` aligned with S-CORE `v1.0`
- Reviewed and updated `packages/version_matrix.bzl`
- Verified generated toolchain repositories for supported platforms
- Successful test workspace smoke-test runs for relevant configurations
- Updated release-facing documentation
- Release notes summarizing supported toolchains, changes, and known limitations

## Validation Expectations
Before closing this issue, verify:
- Bazel module extension usage works for supported toolchains
- Default package resolution is correct for release-targeted versions
- Toolchain registration and platform matching succeed
- Example targets compile and link successfully for the supported matrix
- QNX-specific package/licensing flow is documented and validated as far as release policy allows

## Acceptance Criteria
- A releasable `bazel_cpp_toolchains` version is identified and tagged for S-CORE `v1.0`
- Supported Linux and QNX toolchain configurations are validated in the example workspace
- Package metadata, URLs, checksums, and templates are up to date
- Documentation reflects the final release surface
- Known gaps or unsupported scenarios are explicitly documented

## Checklist
- [ ] Confirm target release version and tag naming
- [ ] Review supported platform/toolchain matrix for `v1.0`
- [ ] Update package metadata as needed
- [ ] Validate Linux host and cross toolchain scenarios
- [ ] Validate runtime-specific Linux variants
- [ ] Validate packaged QNX toolchain scenarios
- [ ] Review templates and generated configuration outputs
- [ ] Update README/docs for the released surface
- [ ] Prepare release notes
- [ ] Publish/tag release