fix(ci): Remove CI/CD check differences between PR and push events

[konard]

Summary

This PR applies best practices from js-ai-driven-development-pipeline-template#18 to fix the issue where CI/CD checks behave differently for pull request events vs push/merge events.

Root Cause

When documentation-only PRs are merged without changelog fragments:

1. The changelog job fails with "No changelog fragment found"
2. The lint job depends on changelog succeeding
3. Ruff/mypy never run on these PRs
4. After merge, the push to main triggers lint, which could fail on unformatted files

Changes

New Script:

• Created scripts/detect_code_changes.py - a cross-platform Python script for detecting file changes in CI/CD
• Replaces need for inline bash scripts for better maintainability and cross-platform support

Workflow Changes:

• Add detect-changes job that runs the new script and outputs what types of files changed
• Make lint job independent of changelog - it's a fast check that should always run
• Make changelog skip for docs-only PRs by adding condition: needs.detect-changes.outputs.any-code-changed == 'true'
• Add || needs.lint.result == 'skipped' and || needs.test.result == 'skipped' to build job to handle the new skipped states
• Update any-code-changed detection to exclude:
  • changelog.d/ folder (changelog metadata)
  • docs/ folder (documentation)
  • experiments/ folder (experimental scripts)
  • examples/ folder (example scripts)
  • All markdown files (*.md) in any folder

Benefits

After this fix:

1. Lint and tests run on ALL PRs regardless of changelog status
2. Docs-only PRs don't require changelog fragments (reducing friction for documentation updates)
3. No differences between PR checks and push/merge checks (preventing future surprises)
4. Changelog validation only runs when code changes (more sensible behavior)
5. Cross-platform compatible - the detection script is written in Python

Testing

Local checks:

• ✅ ruff check . passes
• ✅ ruff format --check . passes
• ✅ mypy src passes
• ✅ pytest tests/ passes

Files Changed

• .github/workflows/release.yml - Workflow structure updates + use new script
• scripts/detect_code_changes.py - NEW Cross-platform change detection script

Fixes #4

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[konard]

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