Fix multi-line Serilog template navigation position calculation

[willibrandon]

Description

Multi-line navigation in the Serilog extension worked but highlighted incorrect arguments due to position calculation errors. Navigation would appear for some properties but select the wrong corresponding arguments because of whitespace and position offset issues in multi-line string templates.

Root cause: Three position calculation issues were causing multi-line navigation failures:

1. Multi-line template detection failed when cursor was positioned on the first line of a multi-line template
2. Template end position calculation returned the position of the closing quote instead of the position after it, causing argument parsing to start at the wrong location
3. Argument parsing was starting from the comma delimiter position instead of after the comma, creating spurious first arguments and shifting all subsequent argument positions

Solution:

• Added fallback to ReconstructMultiLineTemplate() when single-line template detection fails to handle cursors on first line of multi-line templates
• Fixed template end position calculation by changing absolutePosition - 1 to absolutePosition + 1 to point after the closing quote
• Enhanced argument parsing in FindArgumentInMultiLineCall() to find comma delimiter and start parsing from commaIndex + 1 instead of the comma position
• Added test coverage for verbatim strings (@"..."), raw string literals ("""..."""), and regular multi-line string scenarios

Type of change

• Bug fix
• New feature
• Performance improvement
• Documentation update

Checklist

• Tests pass (.\scripts\test.ps1)
• Benchmarks checked (if performance-related)
• Documentation updated (if needed)

Additional notes

Fixes #11

[Copilot]

Pull Request Overview

This PR fixes multi-line Serilog template navigation position calculation issues that caused incorrect argument highlighting. The navigation would appear for some properties but select the wrong corresponding arguments due to whitespace and position offset errors in multi-line string templates.

Key changes include:

• Enhanced multi-line template detection to handle cursors positioned on the first line of multi-line templates
• Fixed template end position calculation to correctly identify where arguments start
• Improved argument parsing to handle comma delimiters properly in multi-line method calls

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
SerilogNavigationProvider.cs	Core navigation logic with multi-line template detection, position calculation fixes, and argument parsing improvements
SerilogClassifier.cs	Added multi-line Serilog call detection to support classification across multiple lines
SerilogNavigationProviderTests.cs	Comprehensive test coverage for multi-line scenarios including verbatim strings, raw string literals, and complex formatting
SerilogClassifierTests.cs	Added test for multi-line LogError classification behavior
ExampleService.cs	Added example of multi-line LogError call for testing purposes

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