Add workspace repo-map manifest for cache/workspace provenance

[christso]

Problem

When AgentV uses hashed local cache paths for repository sources, it's hard to tell which repo/cache key/workspace path corresponds to which source repo and commit during debugging.

Example from eval workspaces:

• workspace repo path: .../workspaces/<id>/shared/CargoWise
• remote origin points to hashed cache path: .../.agentv/git-cache/<hash>

This is correct functionally, but opaque for humans.

Proposal

Auto-generate a workspace manifest that maps each workspace repo to its source/cache details, e.g. repo-map.json (or yaml) in the workspace root.

Suggested fields per repo:

• name (e.g. CargoWise)
• owner / repo
• workspace_path
• cache_path (or cache key)
• remote_url (original upstream if known)
• head_commit (checked-out commit SHA)
• optional: is_shallow, checkout_mode

Why this helps

• Easier debugging of eval runs and cache behavior
• Faster triage when comparing workspace state vs expected source
• Better traceability without needing manual git inspection

Nice-to-have

• Also expose this mapping in trace metadata / eval result metadata.
• Optional naming improvement: prefix cache directories with repo name plus hash for readability.

Thanks!