Enhance code complexity reporting and quality checks

[robgruen]

This pull request migrates the code-quality gates for TypeScript from using a fragile, line-based JSON exceptions file to inline suppression markers, improving maintainability and reducing merge conflicts. The complexity ratchet now relies on stateless HEAD-vs-base diffs to grandfather pre-existing debt, with inline comments as the new mechanism for rare exceptions. Documentation is updated to reflect these changes, and related scripts and CI steps are simplified accordingly.

Migration to inline suppression markers:

• Inline suppression markers replace JSON exceptions for code-complexity, code-lint, and code-debt gates, making exceptions robust to reformatting and file moves; a non-empty reason is now required for each marker. [1] [2]
• JSON exceptions file and update scripts are deprecated/removed: complexity-baseline-exception.json and related update scripts are retired; the --exceptions-file option is now deprecated, and CI/scripts no longer reference it. [1] [2] [3]

Documentation and workflow updates:

• Comprehensive documentation added and updated: DESIGN.md details the rationale, design, and migration plan for inline suppressions; README.md explains how to use inline markers, the stateless grandfathering model, and how to handle exceptions in CI gates. [1] [2] [3]
• CI workflow and error messaging improved: The build workflow and error outputs now reference the new inline suppression mechanism and improved documentation, guiding contributors on exception handling and local reproduction. [1] [2]

Summary of most important changes:

Migration to inline suppressions

• Adopt inline code-<tool>-allow: <reason> markers for complexity, lint, and debt gates, replacing the fragile JSON exceptions file. [1] [2]
• Remove/deprecate the JSON exceptions file and update scripts from the codebase and CI workflow. [1] [2]

Documentation and workflow

• Add detailed design documentation (DESIGN.md) and update main docs to explain the new suppression mechanism and stateless grandfathering. [1] [2] [3]
• Update CI workflow and error messages to reference the new inline suppression approach and improved troubleshooting instructions. [1] [2]