Epic: package registry alpha (signed packages, CLI install, Studio Packages panel) #306

Current State

turian brick manages installed bricks, and the plugin and package epic (#74) is closed. There is no package registry that Turian can query, and Studio has no panel to browse or install packages.

Tasks

• Registry service with signed packages and scoped tokens
• CLI install and update from the registry (turian brick)
• Official packages published and signed by the project
• Studio "Packages" panel reading the registry
• Design note: package overrides and replacement assets, and a compatibility contract for bricks across engine versions (Assets: decide variant, save and mod compatibility contracts #197)
• Free packages only in this epic; paid packages get their own epic later

Acceptance Criteria

• A user installs an official signed package from Studio and from the CLI, and a tampered package is rejected.

Related

#74, #197, brick extraction epic