QueryFindCountJsonResult exposes both 'files' and 'file_count' for the same value

[Widthdom]

Summary

QueryFindCountJsonResult exposes both files and file_count fields that carry the same value. This is internal schema noise that other count-shaped results in the same file (QueryCountFilesJsonResult) avoid.

Evidence

src/CodeIndex/Cli/JsonOutputContracts.cs:35-38:

internal sealed record QueryFindCountJsonResult(
    [property: JsonPropertyName("count")] int Count,
    [property: JsonPropertyName("files")] int Files,
    [property: JsonPropertyName("file_count")] int FileCount);

vs. QueryCountFilesJsonResult (line 30) which uses only files. Both ultimately came from the same total-files count in the underlying query.

Impact

• Clients consuming both count-style commands must handle the inconsistent name.
• New JSON consumers may pick the "wrong" field and silently break later if one is removed.

Proposed direction

1. Decide on file_count (more explicit) or files (shorter, consistent with QueryCountFilesJsonResult).
2. Deprecate the other field in JSON_OUTPUT.md (or wherever the schema is documented) with a removal-version note.
3. Add a CHANGELOG fragment for the deprecation.

Repro env

• Branch: main @ 2ee912d (release v1.21.0)

[Widthdom]

Work started on branch fix-issue1423.