docs: cleanup copilot-instructions.md with dogfooding and coverage validation (#1010)

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: bcollamore <[email protected]>

Author: Copilot

.github/copilot-instructions.md

@@ -54,20 +54,34 @@ dotnet test --configuration Release --logger "trx;LogFileName=test-results.trx"
 
 # 3. Check formatting
 dotnet format style --verify-no-changes --no-restore --verbosity detailed  # NEVER CANCEL: ~23s
+
+# 4. Run dogfooding process (validate analyzers work on own codebase)
+# Use MCP server run_dogfood tool or manual process via CI workflow
+
+# 5. Verify code coverage meets 80% SonarCloud requirement
+# Use MCP server analyze_coverage tool to check coverage gaps
 ```
 
-Total validation time: ~2m 32s - NEVER CANCEL these commands.
+Total validation time: ~2m 32s + dogfood/coverage checks - NEVER CANCEL these commands.
 
 ### Dogfooding Process
 This repository uses a "dogfooding" process where the analyzers analyze their own code:
 - Build creates analyzer packages with `.Dogfood` suffix
 - Analyzers are then applied to the codebase itself
 - All analyzer violations must be fixed, not suppressed
 
+### Code Coverage Requirements
+SonarCloud enforces **80% code coverage** and will fail the build if this threshold is not met:
+- Current coverage is over 90%, so maintain this high standard
+- Use the **MCP server `analyze_coverage` tool** to identify coverage gaps and get actionable suggestions
+- Tool provides specific test templates and prioritizes areas needing coverage
+- Focus testing on error handling, edge cases, and complex logic paths
+
 ### Mandatory CI Requirements
 The CI process enforces these checks that will cause build failures:
 - All tests must pass (1903 tests)
 - Code formatting must be perfect (no deviations from .editorconfig)
+- **80% code coverage minimum** (enforced by SonarCloud)
 - All analyzer warnings must be addressed (no suppressions allowed)
 - Dogfood process must complete successfully
 
@@ -121,7 +135,7 @@ All code MUST strictly follow these .editorconfig rules:
 
 **FORMATTING IS ZERO-TOLERANCE**: Any violation fails the build (IDE0055.severity = error)
 
-**Auto-fix tool available**: Use the MCP server `fix_formatting` tool to auto-correct all formatting issues instead of manual fixes.
+**Auto-fix available**: Use the MCP server `fix_formatting` tool to auto-correct all formatting violations.
 
 ### Creating New Analyzers
 When creating new analyzers:
@@ -144,6 +158,7 @@ Analyzers run during compilation and must be performant:
 - **Title format**: Must follow Conventional Commits (feat:, fix:, docs:, etc.)
 - **All tests pass**: 1903 tests must pass
 - **Formatting perfect**: Zero formatting violations
+- **80% code coverage**: Maintained or improved coverage required
 - **No suppressions**: Fix underlying issues, don't suppress warnings
 - **Documentation**: Update relevant docs in Documentation/ folder
 
@@ -178,22 +193,19 @@ dotnet clean  # Removes packages automatically
 
 ### Troubleshooting
 
-### ⚠️ Formatting Issues (IDE0055)
-**Most common CoPilot failure**: Formatting violations that consume 25% of agent effort.
+### Formatting Issues (IDE0055)
+**Common CoPilot failure**: Formatting violations consume significant agent effort.
 
-**SOLUTION**: Use the MCP server `fix_formatting` tool:
-1. Automatically corrects CRLF line endings (not LF)
-2. Fixes indentation to tabs (not spaces)
-3. Applies all .editorconfig rules
-4. Ensures CI compliance
+**Quick fix**: Use the MCP server `fix_formatting` tool to automatically correct CRLF line endings, tabs, braces, and other .editorconfig violations.
 
 **Manual check**: `dotnet format style --verify-no-changes --no-restore --verbosity detailed`
 
 ### Build Failures
 If builds fail:
-1. Check formatting first: `dotnet format style --verify-no-changes --no-restore --verbosity detailed`
-2. Run clean build: `dotnet clean && dotnet build --configuration Release`
+1. Run clean build: `dotnet clean && dotnet build --configuration Release`
+2. Check formatting: `dotnet format style --verify-no-changes --no-restore --verbosity detailed`
 3. Review analyzer violations - fix the code, don't suppress warnings
+4. Verify code coverage meets 80% requirement
 
 ### Test Failures  
 If tests fail: