[Feature/UX] Add startup pre-flight health check for Node.js runtime to prevent silent hangs when missing

[SagaciousB]

Problem Description

Currently, when a user installs and launches the Eigent desktop client on a machine that does not have Node.js / npm installed (or not in the PATH), the application hangs silently during initialization with no diagnostic error messages or notification boundaries.

This creates significant friction for non-Node developers or enterprise users exploring Eigent for the first time, leading to early drop-off due to perceived instability and immaturity rather than clear prerequisite guidance.

Proposed Solution

1. Startup Pre-Flight Check: Perform a lightweight runtime verification (node -v / npm -v) during initial app bootstrap before spawning dependent worker processes.
2. Graceful Error Boundary: If required runtimes are missing or incompatible, display a clear modal/banner dialog directing the user to exact installation steps or official download links rather than hanging silently.
3. Long-term: Consider bundling lightweight runtime binaries directly with the desktop distribution / installation process so users can achieve zero-prerequisite Time-to-First-Value (TTFV).