v0.2.0: strengthen public positioning, trust, and diagnosis workflows

[noir4y]

Summary

• redesign the public package surface for v0.2.0 with clearer positioning, docs, release notes, and contributor trust material
• add runtime safety controls, retention management, and safer trace persistence defaults
• harden diagnosis output quality, validation response detection, and demo/CI coverage

Changes

• public release surface
  • rewrite README around differentiation, quickstart, examples, screenshots, and comparison guidance
  • add docs for quickstart, production safety, incident walkthroughs, and v0.2.0 release notes
  • add CHANGELOG, SECURITY, CONTRIBUTING, issue templates, PR template, and package metadata
• runtime safety and storage
  • add ROOT_CAUSE_ENABLED and ROOT_CAUSE_RETENTION_DAYS
  • add root-cause:prune, atomic trace writes, temp artifact cleanup, and scoped runtime services
• diagnosis quality
  • improve validation fallback detection across translated/custom 422 payloads
  • normalize file paths, redact sensitive plain exception messages, and stabilize diagnosis serialization
  • add snapshot and regression coverage for validation, exception, and query-pathology incidents
• demo app and CI
  • add an in-repo Laravel 12 demo app for validation, exception, and duplicate query incidents
  • add Laravel 11/12 lockfiles and a GitHub Actions matrix with demo smoke coverage

Commit structure

• 9873bc7 docs: add public release and trust materials
• be61ce3 feat: add runtime safety and trace retention controls
• 4194f5a fix: harden diagnosis outputs and validation detection
• dd6948d test: add demo app smoke coverage and CI matrix
• ee391c9 chore: add demo environment template

Verification

• composer lint
• composer test
• composer analyse

Notes

• PHPUnit still reports 3 existing deprecations during composer test; no new test failures were introduced.