chore: prepare 0.0.19 release cut

[freshtechbro]

Summary

• add post-publish registry-consumer smoke validation and wire it into the public release workflow
• bump package and extension version owners to 0.0.19 and refresh release-facing docs and ledgers
• fix the screencast stop race that could schedule another frame after a first-capture stop request

Testing

• npm run version:check
• node scripts/audit-zombie-files.mjs
• node scripts/docs-drift-check.mjs
• node scripts/chrome-store-compliance-check.mjs
• ./skills/opendevbrowser-best-practices/scripts/validate-skill-assets.sh
• npx opendevbrowser --help
• npx opendevbrowser help
• npm run lint
• npm run typecheck
• npm run test:release-gate
• npm run test
• npm run build
• npm run extension:build
• npm run extension:pack
• npm pack
• node scripts/registry-consumer-smoke.mjs --version 0.0.18 --output /tmp/registry-consumer-smoke-0.0.18.json

Notes

• direct push to protected main was rejected by repo rules, so this release-prep bundle is going through the required PR path
• the only mandatory gate still pending is the real post-publish registry-consumer smoke for 0.0.19 after npm publish