fix(providers): restore http regex and add standalone status code matcher

Restore the http-prefixed regex (without unnecessary (?i) flag since
input is already lowercased by ClassifyError) as a mid-priority pattern
to reduce false positives. Add a standalone word-boundary matcher as a
fallback for bare status codes like "429". Fix test to use lowercased
input matching the actual calling convention.

pkg/providers/error_classifier.go

@@ -9,6 +9,7 @@ import (
 // Common patterns in Go HTTP error messages
 var httpStatusPatterns = []*regexp.Regexp{
 	regexp.MustCompile(`status[:\s]+(\d{3})`),
+	regexp.MustCompile(`http[/\s]+\d*\.?\d*\s+(\d{3})`),
 	regexp.MustCompile(`\b([3-5]\d{2})\b`),
 }
 
@@ -204,7 +205,7 @@ func classifyByMessage(msg string) FailoverReason {
 }
 
 // extractHTTPStatus extracts an HTTP status code from an error message.
-// Looks for patterns like "status: 429", "status 429", "HTTP/1.1 429", "HTTP 429", or standalone "429".
+// Looks for patterns like "status: 429", "status 429", "http/1.1 429", "http 429", or standalone "429".
 func extractHTTPStatus(msg string) int {
 	for _, p := range httpStatusPatterns {
 		if m := p.FindStringSubmatch(msg); len(m) > 1 {

pkg/providers/error_classifier_test.go

@@ -305,7 +305,7 @@ func TestExtractHTTPStatus(t *testing.T) {
 	}{
 		{"status: 429 rate limited", 429},
 		{"status 401 unauthorized", 401},
-		{"HTTP/1.1 502 Bad Gateway", 502},
+		{"http/1.1 502 bad gateway", 502},
 		{"error 429", 429},
 		{"no status code here", 0},
 		{"random number 12345", 0},