[ctawiah]

Context

Repository source links need validated descriptor paths and atomic descriptor storage.

What changes

• Add descriptor paths for variations, tools, and skills.
• Validate repository-relative source paths.
• Read, render, create, and replace descriptors.
• Reject a managed definition when a descriptor already exists.
• Add path, symlink, and atomic update tests.

.launchdarkly/project/configs/support/default.ref.yaml

Design notes

• Existing Phase 1 references remain unchanged.
• The descriptor path supplies the resource identity.

Review focus

• Can a descriptor escape the repository?
• Can one resource have two local definitions?

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. This PR: 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