Extend documentation for the `score_bazel_cpp_toolchains` toolchain model

[nradakovic]

Feature Request / Modification Description

Summary

Expand the repository documentation so the Bazel C/C++ toolchain model is explained in a structured and maintainable way.

Background

The current top-level documentation is too condensed to explain the full toolchain flow clearly. Consumers need separate documentation for the repository layout, module extension API, repository generation flow, validation workspace, QNX-specific behavior, and maintenance expectations.

Scope

This issue covers restructuring and extending the documentation by:

• simplifying the README so it acts as a concise entry point
• moving detailed content into dedicated documentation pages
• documenting the toolchain model and repository responsibilities
• documenting the module extension consumer API
• documenting how repositories are generated from package metadata and templates
• documenting the example workspace and validation intent
• documenting QNX-specific integration details
• documenting repository maintenance expectations

Expected Deliverables

• a concise README that links to the detailed docs
• dedicated docs for:
  • overview
  • repository layout
  • extension API
  • generation flow
  • examples and validation
  • QNX integration
  • maintenance
• removal of outdated or redundant legacy doc structure where no longer needed

Acceptance Criteria

• the README acts as a clear navigation entry point
• detailed toolchain behavior is documented outside the README
• consumers can understand how to declare and use toolchains
• maintainers can understand how package metadata, rules, and templates fit together
• QNX-specific behavior is documented in a dedicated place
• the documentation structure is easier to extend in future releases

Notes

This issue is about documentation structure and clarity. It should not change the functional toolchain behavior.

Expected Changes ot work products

• Requirements
• Architecture
• Safety Analysis
• Security Analysis
• Detailed Design
• Implementation and Testing
• all

Impact analysis

None

Safety or Security relevance

• none
• Safety relevant
• Security relevant

Expected required ASIL classification

QM

Expected Implementation Version (Release)

No response