Add ConfiginfoBuilder for simplified cross-platform configuration with zero-configuration pattern and comprehensive project metadata extraction (#157)

* Initial plan

* Add ConfiginfoBuilder class with comprehensive tests

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add comprehensive usage documentation for ConfiginfoBuilder

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Extract default black formats as public constant per code review

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add example code demonstrating ConfiginfoBuilder usage

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add comprehensive README for ConfiginfoBuilder feature

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Use host app's base directory for InstallPath default

Changed default InstallPath from %APPDATA%/~/.config to AppDomain.CurrentDomain.BaseDirectory. This:
- Extracts path from host program's runtime location
- Requires no admin privileges (uses app's own directory)
- Aligns with existing codebase pattern (Thread.GetDomain().BaseDirectory)
- More universal and highly available across deployments

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add ConfiginfoBuilder link to GeneralUpdate.ClientCore project

The ConfiginfoBuilder is primarily used in client-side update scenarios, so it should be available in GeneralUpdate.ClientCore in addition to GeneralUpdate.Core.

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add Velopack-inspired factory method and improve documentation

- Added ConfiginfoBuilder.Create() factory method for more fluent API
- Updated documentation to mention Velopack zero-configuration inspiration
- Added tests for factory method (34/34 tests passing)
- Enhanced XML documentation with references to zero-configuration patterns

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add macOS platform support to ConfiginfoBuilder

- Added InitializeMacOSDefaults() method for macOS-specific configuration
- macOS uses Unix-like defaults (no .exe extension, chmod script)
- Updated platform detection to check for OSPlatform.OSX
- Added macOS test case (35/35 ConfiginfoBuilder tests passing)
- Updated documentation to include macOS platform details
- All tests passing: 60/60 CoreTest, 35/35 ConfiginfoBuilder

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add automatic application name extraction from csproj files

- Implemented TryExtractApplicationNameFromProject() to read app name from .csproj
- Searches up to 3 parent directories for project file
- Extracts <AssemblyName> property or falls back to csproj filename
- Applies platform-specific extensions (.exe on Windows, none on Linux/macOS)
- Added test for project file extraction functionality (36/36 tests passing)
- Updated documentation to explain auto-discovery feature
- All tests passing: 61/61 CoreTest, 36/36 ConfiginfoBuilder

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add comprehensive project metadata extraction (version, company/authors)

- Enhanced TryExtractProjectMetadata() to extract multiple fields from .csproj
- Extracts <Version> field and maps to ClientVersion/UpgradeClientVersion
- Extracts <Company> or <Authors> fields and maps to ProductId
- Refactored to use ProjectMetadata class for cleaner code organization
- Added ExtractXmlElement() helper for consistent XML parsing
- Updated all platform initialization methods to use metadata
- Added test for project metadata extraction (37/37 tests passing)
- Updated documentation with comprehensive metadata extraction table
- All tests passing: 62/62 CoreTest, 37/37 ConfiginfoBuilder

Addresses @JusterZhu's specification for extracting:
1. App Name from <AssemblyName> ✓
2. Version Number from <Version> ✓
3. Publisher from <Company>/<Authors> ✓

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

Author: Copilot