[ctawiah]

Context

Detach must remove descriptor state without editing or deleting the referenced source.

What changes

• Delete a descriptor when it defines the selected resource.
• Keep managed-file detach behavior.
• Reject conflicting descriptor and managed definitions.
• Leave external source bytes unchanged.
• Add detach and source-preservation tests.

descriptor removed
source unchanged

Design notes

• Deletion uses the existing staged rollback path.
• Missing or conflicting definitions fail before mutation.

Review focus

• Can detach delete an external source?
• Does rollback preserve descriptor state after failure?

Verification

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

Related changes

1. ctawiah/sync-projection-core-3bbf: 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. This PR: 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