Add QEG CI cumulative report demo

[RNA4219]

Summary

• add a GitHub Actions CI workflow that runs diagnostics with continue-on-error and uploads .qeg/qeg-ci-report.json
• add qeg report for cumulative CLI error, DQ, blocker, residual risk, and human-review reporting
• document manual workflow_dispatch demo with qeg_report_targets=fixtures/negative-approval-missing

Verification

• npm run typecheck
• npm run build
• npm run report -- --json --out .qeg/qeg-ci-report.json fixtures/positive-release-go
• node dist/cli.js report --json --out .qeg/demo-fail-report.json fixtures/negative-approval-missing
• npm pack --dry-run --cache ./.npm-cache
• full fixture gate expected exit-code regression