Add map section controls and deps graph exports

[Widthdom]

Summary

• Add map section selection and module depth controls for CLI and MCP callers.
• Add deps graph export formats and cycle-only output for CLI and MCP callers.
• Add changelog fragments and focused parser/cycle tests.

Fixes #1634
Fixes #1635

Validation

• dotnet build CodeIndex.sln -c Release -p:UseSharedCompilation=false
• dotnet run --project tools/CodeIndex.Changelog -- check
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj -c Release --filter "FullyQualifiedName~QueryCommandRunnerTests" -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj -c Release --filter "FullyQualifiedNameQueryCommandRunnerTests.RunMap_ParseSectionsAndDepth_StoresSelectors|FullyQualifiedNameQueryCommandRunnerTests.ParseArgs_GraphFormatOutsideDeps_ReturnsParseError|FullyQualifiedName~QueryCommandRunnerTests.FindDependencyCycles_ReturnsStronglyConnectedFileComponents" -p:UseSharedCompilation=false
• CLI smoke: map --json --sections languages,metrics --depth 1; deps --format dot; deps --json --cycles

Review

No blocking/actionable issues found.