Add a root README that explains the active runtime layers and onboarding path, and keep local OMX session state out of version control so developer tooling does not interfere with pulls.
Constraint: Local OMX state is developer-specific and should not block branch sync or appear in shared history
Rejected: Keep onboarding notes untracked | easy to lose and hard to share with the team
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: Keep the README aligned with the active app/backend-java/frontend-vue execution path; revisit if the runtime architecture changes
Tested: git diff review; git status after staging
Not-tested: lint, typecheck, unit/integration tests not run (docs and ignore rules only)
