Clarify local Connect development

[callumalpass]

What changed

• separate the localhost full-stack workflow from managed Connect
• document how to start and pair the isolated local control plane and desktop profile
• point the SDK client at the local Connect server when the app runs on loopback
• clarify that --allow-local belongs only to static manifest validation
• document the HTTPS manifest changes required for the managed service

Why

The previous quickstart combined a localhost manifest with https://connect.mdbase.dev. The managed service rejects HTTP manifests, so the copy-paste example could not complete authorization even though the local validator accepted it.

Developer impact

Developers now get one complete local workflow and a distinct production deployment path, without implying that the desktop application exposes an --allow-local switch.

Checks

• pnpm test
  • Astro check: 0 errors, warnings, or hints
  • production build: 24 pages
  • specification import
  • local link and prose checks: 26 HTML files