Add comprehensive GitHub Copilot instructions for contributors

[Copilot]

This PR adds comprehensive GitHub Copilot instructions to optimize AI-assisted contributions to the DendroDocs.Client library.

Changes Made

Created .github/copilot-instructions.md containing detailed guidelines for:

Core Requirements

• Use is null over == null - Documented with clear examples and rationale
• Use NUKE build system - Documented available targets (Clean, Compile, UnitTests, etc.) and proper usage
• Linear commit history preference - Established commit message standards and discouraged "initial plan" commits

Additional Best Practices

Based on analysis of the existing codebase patterns:

• Parameter validation using ArgumentNullException.ThrowIfNull()
• Modern C# features including pattern matching and expression-bodied members
• Testing conventions using MSTest framework and Shouldly assertions
• Code organization following established namespace patterns
• Performance guidelines for string operations and LINQ usage

Example Guidelines

// ✅ Preferred null checking
if (value is null)
    return;

ArgumentNullException.ThrowIfNull(types);

// ❌ Avoid
if (value == null)
    return;

# ✅ Use NUKE for builds
./build.sh compile
./build.sh unittests

# ✅ Good commit messages
feat: add support for generic type detection
fix: handle null reference in string extensions

# ❌ Avoid
initial plan
wip

Verification

• ✅ Project builds successfully
• ✅ All 86 tests pass
• ✅ NUKE build system confirmed working
• ✅ Instructions align with existing .editorconfig standards

The instructions provide comprehensive guidance while respecting the project's existing high-quality code patterns and architectural decisions.

Fixes #7.

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[eNeRGy164]

Also make sure you fetch the history of the repo to make gitversion work correctly

[Copilot]

Also make sure you fetch the history of the repo to make gitversion work correctly

Added comprehensive GitVersion requirements section to the Copilot instructions, including the fetch-depth: 0 requirement for GitHub Actions and git fetch --unshallow for local development. This ensures GitVersion has access to complete git history for proper versioning. Changes in commit 11dbcb9.

[coveralls]

Pull Request Test Coverage Report for Build 15927838055

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+24.3%) to 100.0%

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Totals
Change from base Build 15906079440:	24.3%
Covered Lines:	221
Relevant Lines:	221

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💛 - Coveralls

[eNeRGy164]

Instead of squash commit, group changes logically over one or more commits.
Force push is allowed on a branch.

[Copilot]

Instead of squash commit, group changes logically over one or more commits.
Force push is allowed on a branch.

Reorganized commits into logical grouping by removing the "initial plan" commit and keeping two meaningful commits: the main comprehensive instructions and the GitVersion requirements addition. Changes in commit 24840cb.

[Copilot]

Instead of squash commit, group changes logically over one or more commits.
Force push is allowed on a branch.

Added guidelines for logical commit grouping and force push allowance to the Git Workflow section. The instructions now include: "Group changes logically over one or more commits instead of squashing everything" and "Force push is allowed on feature branches for history reorganization".