Implement CI/CD with static analysis and tests for increased code reliability

[fibonatto]

Problem

The project currently lacks Continuous Integration / Deployment (CI/CD) workflows and static analysis checks. This increases risk of regressions, undetected errors, and inconsistent code quality. Without CI:

• Pull requests can accidentally break critical paths (parser, renderer, build pipeline)
• Bugs in C code (buffer overflows, undefined behavior) remain undetected
• Formatting, lint, and code health are not enforced
• Fuzz regression and e2e tests are not automated

Proposed Solution

• Add a GitHub Actions workflow for PRs and pushes:
  • Build for all major platforms (Linux, macOS)
  • Run static analysis (clang-tidy, cppcheck, etc.)
  • Run all existing (and newly created) tests (fuzz, regression, e2e)
  • Optionally check formatting (clang-format)
• Add status badge to README
• Document the pipeline for contributors

Acceptance Criteria

• PRs fail if any test or analysis fails
• CI jobs cover all core C source and test code
• Static analysis issues are surfaced before merge

References

• https://github.com/marketplace/actions/clang-tidy-review
• https://github.com/google/oss-fuzz
• https://github.com/actions/setup-python