fix(sonarcloud): add .sonarcloud.properties for automatic analysis (#158)

Automatic analysis ignores sonar-project.properties.
Create .sonarcloud.properties with explicit test exclusion
to fix Quality Gate duplication failure.

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Model-Raw: claude-opus-4-5-20251101

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: nullvariant

.sonarcloud.properties

@@ -0,0 +1,20 @@
+# SonarCloud Automatic Analysis Configuration
+# https://docs.sonarsource.com/sonarqube-cloud/advanced-setup/automatic-analysis/
+#
+# NOTE: This file is for automatic analysis (GitHub App).
+# Wildcard patterns are NOT allowed in this file.
+# sonar-project.properties is IGNORED when using automatic analysis.
+
+# Source and test directories (explicit paths, no wildcards)
+sonar.sources=extensions/git-id-switcher/src
+sonar.tests=extensions/git-id-switcher/src/test
+
+# Exclusions from source analysis
+sonar.exclusions=extensions/git-id-switcher/src/test
+
+# Exclude test directory from duplication detection
+# Test code intentionally has duplication for readability and isolation
+sonar.cpd.exclusions=extensions/git-id-switcher/src/test
+
+# Source encoding
+sonar.sourceEncoding=UTF-8