Address CLI audit output issues

[Widthdom]

Summary

• Centralize duplicated CLI stdout/stderr/warning output writing for the affected command runners.
• Add map --summary-only for aggregate-only JSON payloads.
• Clarify unused audit filters and add compact JSON output with filter context.
• Add symbols --sort hotspot|references|size|complexity|path with JSON ranking metadata.

Validation

• dotnet build CodeIndex.sln -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~QueryCommandRunnerTests.RunMap_ -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~QueryCommandRunnerTests.RunUnused_ -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~QueryCommandRunnerTests.RunSymbols_ -p:UseSharedCompilation=false
• dotnet run --project tools/CodeIndex.Changelog -- check
• git diff --check
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll map --summary-only --json --limit 1
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll unused --compact --bucket likely_unused_private --min-confidence medium --limit 3
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll symbols --sort hotspot --json --limit 1
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll index . --commits HEAD --json
• Codex adversarial review: No blocking/actionable issues found.

Documentation And Changelog

• Updated USER_GUIDE.md for the new map, unused, and symbols CLI behavior.
• Added changelog fragments:
  • changelog.d/unreleased/3417.internal.md
  • changelog.d/unreleased/3393.added.md
  • changelog.d/unreleased/3395.changed.md
  • changelog.d/unreleased/3451.added.md

Follow-Up Candidates

• None.

Fixes #3417
Fixes #3451
Fixes #3395
Fixes #3393