feat(rules): add C# language support (#704)

* feat(rules): add C# language support

* feat: add everything-claude-code ECC bundle (#705)

* feat: add everything-claude-code ECC bundle (.claude/ecc-tools.json)

* feat: add everything-claude-code ECC bundle (.claude/skills/everything-claude-code/SKILL.md)

* feat: add everything-claude-code ECC bundle (.agents/skills/everything-claude-code/SKILL.md)

* feat: add everything-claude-code ECC bundle (.agents/skills/everything-claude-code/agents/openai.yaml)

* feat: add everything-claude-code ECC bundle (.claude/identity.json)

* feat: add everything-claude-code ECC bundle (.codex/agents/explorer.toml)

* feat: add everything-claude-code ECC bundle (.codex/agents/reviewer.toml)

* feat: add everything-claude-code ECC bundle (.codex/agents/docs-researcher.toml)

* feat: add everything-claude-code ECC bundle (.claude/rules/everything-claude-code-guardrails.md)

* feat: add everything-claude-code ECC bundle (.claude/research/everything-claude-code-research-playbook.md)

* feat: add everything-claude-code ECC bundle (.claude/team/everything-claude-code-team-config.json)

* feat: add everything-claude-code ECC bundle (.claude/enterprise/controls.md)

* feat: add everything-claude-code ECC bundle (.claude/commands/database-migration.md)

* feat: add everything-claude-code ECC bundle (.claude/commands/feature-development.md)

* feat: add everything-claude-code ECC bundle (.claude/commands/add-language-rules.md)

---------

Co-authored-by: ecc-tools[bot] <257055122+ecc-tools[bot]@users.noreply.github.com>

* ci: retrigger

---------

Co-authored-by: ecc-tools[bot] <257055122+ecc-tools[bot]@users.noreply.github.com>

rules/csharp/testing.md

@@ -0,0 +1,46 @@
+---
+paths:
+  - "**/*.cs"
+  - "**/*.csx"
+  - "**/*.csproj"
+---
+# C# Testing
+
+> This file extends [common/testing.md](../common/testing.md) with C#-specific content.
+
+## Test Framework
+
+- Prefer **xUnit** for unit and integration tests
+- Use **FluentAssertions** for readable assertions
+- Use **Moq** or **NSubstitute** for mocking dependencies
+- Use **Testcontainers** when integration tests need real infrastructure
+
+## Test Organization
+
+- Mirror `src/` structure under `tests/`
+- Separate unit, integration, and end-to-end coverage clearly
+- Name tests by behavior, not implementation details
+
+```csharp
+public sealed class OrderServiceTests
+{
+    [Fact]
+    public async Task FindByIdAsync_ReturnsOrder_WhenOrderExists()
+    {
+        // Arrange
+        // Act
+        // Assert
+    }
+}
+```
+
+## ASP.NET Core Integration Tests
+
+- Use `WebApplicationFactory<TEntryPoint>` for API integration coverage
+- Test auth, validation, and serialization through HTTP, not by bypassing middleware
+
+## Coverage
+
+- Target 80%+ line coverage
+- Focus coverage on domain logic, validation, auth, and failure paths
+- Run `dotnet test` in CI with coverage collection enabled where available