fix: handle Windows service install paths

[joeynyc]

Summary

• Fix Windows Task Scheduler service install by passing schtasks arguments via execFileSync instead of a composed cmd.exe string.
• Use the current CLI entrypoint as the service script path instead of constructing a nested lib/node_modules/... path.
• Stop reporting a successful Windows service install when schtasks /create fails.
• Add tests for installed entrypoint path handling and Windows task command construction.

Root cause

The Windows install path was fragile in two ways: paths containing spaces were interpolated into a shell command string for schtasks, and getDistPath() could turn an already-valid dist/index.js entrypoint into a non-existent nested npm global path.

Fixes #13.

Validation

• npm test -- src/cli/service.test.ts
• npm run typecheck
• npm test
• npm run build