feat: add the generate-editor-search-query skill

[ziyiunity]

Adds generate-editor-search-query — generates Unity Search / Quick Search queries and opens the Search window pre-populated. 3 files.

Why this changed

Written for Unity AI Assistant, where a built-in tool ran C# in the Editor. That tool does not exist in a third-party coding agent, so the three references to it now point at the Unity CLI (unity command eval), and the Editor-side snippet lost its IRunCommand wrapper. description is byte-identical; the query-generation rules are untouched.

The one constraint that shapes the snippets

eval compiles a statement block, not a file. using UnityEditor; inside a method body is read as a resource-disposal statement rather than a namespace import, so it fails outright (CS0210) — and with no import, short type names are unknown (CS0246) and a bare Object is ambiguous with object (CS0104).

So snippets meant for eval are fully qualified and carry no usings. Snippets meant to be saved into the project as a .cs file keep their usings and short names, because that is correct for a file. Every eval-destined snippet here was compile-checked against a live Unity 6 Editor, by prefixing it with an unreachable early return so it type-checks without executing.

What changed specifically

• The IRunCommand class in references/open-search-window.md became a plain snippet, fully qualified — UnityEditor.Search.SearchService, System.Linq.Enumerable.Where/ToArray rather than LINQ extension syntax, since there is no using System.Linq.
• result.Log("Opened Unity Search with query: {0}", query) became a return — through the CLI, logs go to the Editor console and the caller never sees them.
• Three prose references to the old tool now describe the action instead ("open Unity Search by running the Editor-side snippet"), and prerequisites are delegated to the unity-cli skill rather than restated.
• Added a note that if eval is unavailable, the skill should still generate the query text and say the window can't be opened — the query is useful on its own.

Tested

The search-window snippet compiles cleanly against a live Editor. Its read-only nature is preserved: the skill states this must not create, modify, delete, import, install or save anything.

What would be most useful to review

The query patterns in references/query-patterns.md. Unity Search syntax is the part that goes stale, and it's unchanged from your original.