Trim-safe QueryCommandRunner JSON outputs

[Widthdom]

Summary

This PR addresses the follow-up candidates called out in PR #1074.

• Replace remaining QueryCommandRunner anonymous JSON payloads with source-generated DTOs or JsonObject builders.
• Add a trimmed-publish regression for search, find, and validate JSON output.
• Add a bilingual changelog fragment under changelog.d/unreleased/1074.fixed.md.

Validation

• dotnet build
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~RunPublishedTrimmedCli_SerializesQueryJsonAndErrorJson
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~RunLanguages_JsonListsModernNodeModuleExtensions
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll index . --files src/CodeIndex/Cli/QueryCommandRunner.cs src/CodeIndex/Cli/JsonOutputContracts.cs tests/CodeIndex.Tests/QueryCommandRunnerTests.cs CHANGELOG.md --json
• dotnet build after commit
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll index . --commits HEAD --json after commit

Documentation / Changelog

• Added changelog.d/unreleased/1074.fixed.md in both English and Japanese.
• Removed the direct CHANGELOG.md entries so release prep can aggregate the fragment instead.

Follow-up candidates

• QueryCommandRunner still has other non-anonymous JSON output helpers that may need the same trim-safe treatment if trimmed-build JSON support is expanded further.

[Widthdom]

Working on the follow-up candidates from this PR now. I’m starting from the latest origin/main, will keep the changes focused, and will update this PR with the implementation and validation results.

[Widthdom]

Follow-up candidates from this PR have been addressed in PR #1108.

Implemented:

• replaced the remaining anonymous QueryCommandRunner JSON payloads with DTOs / JsonObject builders
• added a trimmed-publish regression for the JSON count paths and missing-file outline error
• added a bilingual fragment at changelog.d/unreleased/1103.fixed.md