Fix C# references, symbol ranges, and inspect file-line mode

[Widthdom]

Summary

• Suppress common receiver-qualified C# member-call overmatches such as Path.Combine, Math.Max, and JsonElement.GetString while preserving direct and this. calls.
• Add regression coverage that locks tight C# method ranges near local functions, lambdas, generic helpers, and later members.
• Make inspect --path --line resolve the exact symbol on definition lines or the smallest enclosing symbol on body lines, returning definitions and nearby_symbols instead of only a source excerpt.
• Merged latest origin/main and updated the legacy Show source excerpts and line ranges from cdidx inspect #3786 path-line inspect test expectation that was failing CI after the Make inspect file-line mode return the exact or enclosing symbol #3915 behavior change.

Validation

• dotnet build -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~Issue3786 -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~Issue3894 -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~Issue3912 -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~Issue3915 -p:UseSharedCompilation=false
• dotnet run --project tools/CodeIndex.Changelog -- check
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll status --check --json
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll inspect --path src/CodeIndex/Cli/QueryCommandRunner.cs --line 3120 --json --limit 3

Changelog

• changelog.d/unreleased/3894.fixed.md
• changelog.d/unreleased/3912.fixed.md
• changelog.d/unreleased/3915.fixed.md

Notes

• No requested issue was excluded for an existing work-start comment.
• AGENT.md, CLAUDE.md, and AGENT_GUIDE.md were not modified by this PR diff against latest origin/main.
• Adversarial review result: No blocking/actionable issues found.

Fixes #3894
Fixes #3912
Fixes #3915