ci: move coverage validation to separate script for better readability

scripts/check-coverage.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+# Check test coverage against minimum threshold
+
+set -e
+
+COVERAGE_FILE="${1:-.build/coverage.out}"
+MIN_COVERAGE="${2:-80}"
+
+if [ ! -f "$COVERAGE_FILE" ]; then
+    echo "Error: Coverage file not found: $COVERAGE_FILE"
+    exit 1
+fi
+
+# Extract coverage percentage using awk
+COVERAGE=$(go tool cover -func "$COVERAGE_FILE" | awk '/^total:/ { match($0, /[0-9.]+%/); print substr($0, RSTART, RLENGTH-1) }')
+
+echo "Total coverage: ${COVERAGE}%"
+
+# Compare as integers (remove decimals for simpler comparison)
+COVERAGE_INT=${COVERAGE%.*}
+
+if [ "$COVERAGE_INT" -lt "$MIN_COVERAGE" ]; then
+    echo "Coverage ${COVERAGE}% is below minimum ${MIN_COVERAGE}%"
+    exit 1
+fi
+
+echo "Coverage check passed"
+exit 0