[ctawiah]

Context

Repository adapters need shared projections, capabilities, structured errors, and lock metadata before any format can use them.

What changes

• Add typed variation, tool, and skill projections.
• Add mapped-field capabilities and projection fingerprints.
• Add structured sync problems with stable codes and suggestions.
• Add adapter metadata to lock format version 1.

prompt: direct
tools: read-only

Design notes

• This change is additive. Existing Phase 1 references keep their current behavior.
• Later changes consume these shared types.

Review focus

• Do projections cover each mapped field?
• Do problems carry enough data for plain text and JSON output?

Verification

• make build
• go test ./...
• Repository lint
• Relevant race tests

Related changes

1. This PR: projection and problem core
2. ctawiah/sync-reference-core-3bbf: reference registry and Markdown
3. ctawiah/sync-structured-adapters-3bbf: structured adapters
4. ctawiah/sync-provider-profiles-3bbf: provider profiles
5. ctawiah/sync-python-adapter-3bbf: Python adapter
6. ctawiah/sync-typescript-adapters-3bbf: TypeScript and JavaScript adapters
7. ctawiah/sync-descriptor-storage-3bbf: descriptor storage
8. ctawiah/sync-source-publication-3bbf: source compilation and publication
9. ctawiah/sync-source-planner-3bbf: planner integration
10. ctawiah/sync-descriptor-detach-3bbf: descriptor detach
11. ctawiah/sync-link-preparation-3bbf: link preparation
12. ctawiah/sync-link-command-3bbf: link commands
13. ctawiah/sync-reference-cleanup-3bbf: Phase 1 cleanup