Agent Prep without source checkout

[BramVR]

Parent

#70

What to build

Allow agent prepare to prepare a workspace from registered Project identity and clone URL when the local source checkout is missing and enough registry/manifest information exists. The path remains missing locally; no fake project directory is created.

Acceptance criteria

• Missing source checkout is not automatically a blocker when registered clone data is sufficient for remote handoff.
• Agent Prep still blocks on missing clone data, origin ambiguity, fetch failure, and missing base.
• Env file checks degrade safely when local source checkout is absent.
• Agent Run Contract records that source checkout was absent.
• Tests and e2e cover missing local path handoff without creating placeholder directories.

Blocked by

• Git Operations and Project identity locality #71
• Shared Readiness Decision for existing commands #72
• Agent Run Contract v1 baseline #73
• Base selection and checkout provenance #77