Bootstrap `.protobot` projects and governed Git workflow

Scope

Implement project initialization and the first governed Git path: .protobot/project.yaml, artifact registration, spec-store paths, schema versions, project validation, branch creation, commit preparation, and reviewable PR preparation.

Use a local bare-repository fixture. ears-manager owns registered specification writes; the Drafting Table owns explicit Git operations around those writes.

Dependencies

• #30 and #34.
• ears-manager core CLI child issue.

Acceptance criteria

• A fixture project can be initialized, validated, branched, and committed.
• Registered specification files cannot be modified through an ungoverned path without CI or validation detecting it.
• Single-player and multi-player flows differ only in review ceremony.
• Missing paths, invalid configuration, Git failures, and partial operations return deterministic diagnostics.

Start by reviewing dependencies #30 and #34 and the ears-manager core CLI child issue. Map the initialization flow around .protobot/project.yaml, artifact registration, spec-store paths, and the Drafting Table’s explicit Git operations, using a local bare-repository fixture. Done means the fixture can initialize, validate, branch, commit, and report deterministic diagnostics for invalid or partial operations.