Add integration tests with real xcresult fixtures

- Update IntegrationTests.swift to use fixture bundles via Bundle.module
- Remove .disabled attribute and environment variable dependency
- Add 4 xcresult bundles: clean build, errors, warnings+failures, analyzer
- Fix BuildIssue severity mapping to use contains() for partial matches
- All 39 tests now passing (35 unit + 4 integration)

Author: diogot

Sources/XCResultParser/Models/BuildIssue.swift

@@ -28,11 +28,13 @@ public struct BuildIssue: Sendable, Codable, Equatable {
 
     /// Severity level for annotations based on issue type
     public var severity: Severity {
-        switch issueType.lowercased() {
-        case "error": .failure
-        case "warning": .warning
-        case "analyzer warning": .warning
-        default: .notice
+        let lowercased = issueType.lowercased()
+        if lowercased.contains("error") {
+            return .failure
+        } else if lowercased.contains("warning") {
+            return .warning
+        } else {
+            return .notice
         }
     }
 }

Tests/XCResultParserTests/Fixtures/analyzer-warnings-only.xcresult/Data/data.0~0uY4S88M6rJdqpEUD-V73bhY3Zkkw0pkz9-hj0tQaTDNmiUSe89bA0ARP_43rbR5Keb71mxUCJWNsPZqyv4sdg==

@@ -0,0 +1 @@
+[]