fix(health): use ordered slice for error pattern matching

The formatErrorSummary function used a map for error pattern matching,
but Go map iteration order is non-deterministic. This caused flaky test
failures when error messages matched multiple patterns (e.g., 'dial tcp:
no such host' matches both 'dial tcp' and 'no such host').

Changed to an ordered slice where more specific patterns (like 'no such
host') are checked before generic ones (like 'dial tcp').

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: technicalpickles

internal/health/calculator.go

@@ -204,25 +204,33 @@ func formatErrorSummary(lastError string) string {
 		return "Connection error"
 	}
 
-	// Common error patterns to friendly messages
-	errorMappings := map[string]string{
-		"connection refused":     "Connection refused",
-		"no such host":           "Host not found",
-		"connection reset":       "Connection reset",
-		"timeout":                "Connection timeout",
-		"EOF":                    "Connection closed",
-		"authentication failed":  "Authentication failed",
-		"unauthorized":           "Unauthorized",
-		"forbidden":              "Access forbidden",
-		"oauth":                  "OAuth error",
-		"certificate":            "Certificate error",
-		"dial tcp":               "Cannot connect",
+	// Common error patterns to friendly messages.
+	// Order matters: more specific patterns must come before generic ones.
+	// For example, "no such host" must be checked before "dial tcp" since
+	// DNS errors often appear as "dial tcp: no such host".
+	errorMappings := []struct {
+		pattern  string
+		friendly string
+	}{
+		// Specific patterns first
+		{"no such host", "Host not found"},
+		{"connection refused", "Connection refused"},
+		{"connection reset", "Connection reset"},
+		{"timeout", "Connection timeout"},
+		{"EOF", "Connection closed"},
+		{"authentication failed", "Authentication failed"},
+		{"unauthorized", "Unauthorized"},
+		{"forbidden", "Access forbidden"},
+		{"oauth", "OAuth error"},
+		{"certificate", "Certificate error"},
+		// Generic patterns last
+		{"dial tcp", "Cannot connect"},
 	}
 
-	// Check for known patterns
-	for pattern, friendly := range errorMappings {
-		if containsIgnoreCase(lastError, pattern) {
-			return friendly
+	// Check for known patterns (in order)
+	for _, mapping := range errorMappings {
+		if containsIgnoreCase(lastError, mapping.pattern) {
+			return mapping.friendly
 		}
 	}