[E-4] Install & DX Polish

[LennyObez]

Epic | P1 | Risk: Medium | Effort: L | Release: 1.0.0

The hello-world example is unverified. bin/pulsar init scaffold flow is unverified. No Getting Started guide exists for new users.

Scope:

• Verify hello-world example runs correctly
• Verify bin/pulsar init scaffold flow
• Verify multi-environment presets (dev/staging/prod)
• Write Getting Started tutorial

Acceptance criteria:

• Hello-world example runs and all routes respond correctly
• Init scaffold completes within 60s target
• Environment presets work correctly
• Getting Started guide is complete and tested