feat(engine): make AddNode non-blocking with async node creation #1043

Job	Run time
E2E / Playwright E2E	18m 0s
UI / Lint (TypeScript + ESLint)	37s
UI / Knip (unused code)	20s
UI / Test	22s
Skit / Lint (fmt + clippy)	4m 13s
Skit / Test	9m 17s
UI / Build	17s
Plugins / Lint (Simple Plugins)	1m 0s
Skit / Test (GPU)	2m 39s
Plugins / Lint (Whisper)	37s
Skit / Build	12m 18s
Plugins / Format Check	19s
Plugins / Lint (NLLB)	2m 12s
Plugins / Lint (Sherpa-ONNX Plugins)	47s
All Checks Passed	2s
	53m 0s

Provide feedback