Release v0.1.19

[marcelormendes]

Summary

• contain persistent xterm surfaces so terminal dimensions cannot feed back into Herdr
• use xterm's reliable DOM renderer instead of the crashing WebGL addon
• retain the canonical workspace across transient background bootstrap failures
• bump Drover to v0.1.19

Verification

• npm run verify: 64 test files, 553 tests passed
• packaged Electron smoke against an isolated Herdr v0.8.3 server
• 50 resize cycles stayed bounded and live terminal output continued
• current packaged-process logs contained no renderer errors