First-class sidecar annotations file (openshell.annotations.yaml) #20

Summary

Teams that cannot or do not want to edit source (vendored code, third-party repos, generated code, Paperclip-style test cases) need a first-class way to keep directives outside the code.

Proposal

• Optional file openshell.annotations.yaml that the scanner merges with inline comments.
• Entries anchor to a file and symbol (for example src/llm.ts#callOpenAI), with a line number only as a fallback.
• lint and drift fail when an anchor no longer resolves.
• diff-logs --write can target either the source comments or the sidecar file.

Today

A .sh sidecar file with @openshell comments works as a workaround (pocketrb). Related: #7 (extra comment leaders for unsupported languages).