Initialize `.protobot` projects and the artifact registry

Plan ID

EM-06

Purpose

Provide the first usable project bootstrap path around the ears-manager CLI.

Scope

• Initialize .protobot/project.yaml through the governed ears-manager operation defined by #30.
• Seed schema versions, project identity, canonical repository settings, and default artifact registrations.
• Register requirement-store and change-set paths with safe path and ownership checks.
• Write the corresponding shared entries in .protobot/projection.yaml for registered specification paths.
• Validate adoption of an existing repository without rewriting unrelated history.

Dependencies

Depends on #30 and EM-04. The completed Git contract is #34; it is not a blocker.

Acceptance criteria

• Initialization rejects empty repositories, misplaced project files, unsafe paths, credentials, and invalid registry entries.
• A fixture project can be initialized and then passes ears-manager check.
• Registration and projection updates are atomic from the caller's perspective.
• Existing files are registered without being moved or rewritten.
• Tests cover missing paths, invalid configuration, schema mismatch, digest handling, and retry after failure.

Out of scope

Branch, commit, and pull-request preparation belong to EM-07.

Start by reading dependency #30 and EM-04, then trace the ears-manager initialization operation and the .protobot/project.yaml and .protobot/projection.yaml formats. Use a fixture project and run ears-manager check while covering the listed failure cases. Done means safe initialization, registration, and projection updates work atomically without rewriting existing files.