v4.8.3: Clear SonarCloud new-code issues

Fixes the 4 reported bugs and ~97 code smells flagged in the new-code
period. No behavior changes.

Bugs (swift:S3923) — DomainInspectionService's confidenceFor* helpers each
returned `error == nil ? .low : .low`, an inert conditional. Simplified to
`return .low` and dropped the now-unused `error` parameter.

Smells:
- Merged 14 identical `.empty`/`.error` switch branches in DomainViewModel
- Consolidated duplicate implementations (clearPresentedResults/reset,
  String.nonEmpty/nilIfEmpty, ExportFormat.id/fileExtension)
- Extracted nested ternaries into TLSGrade.tone, EmailSecurityGrade.tone,
  and ChangeImpactClassification.color; removed ContentView.impactColor
  and the duplicate mapping in BatchResultsView
- Documented empty closures and singleton inits
- Marked unused protocol-conformance parameters `_`
- Renamed CloudSyncTrigger.`import` to `imported` (raw value preserved)
  and SSLSessionDelegate's _serverTrust/_tlsMetadata
- Merged nested ifs in the DER parser; flattened closure nesting in
  PortScanService and IntegrationService
- Replaced two-case switches with if/else

Left open: S107 (init parameter counts), S115 (constants mirroring DoH and
ipapi JSON keys), S1075 (false positives on https:// literals), and two
S117 hits on SwiftUI $binding shorthand. These want a Won't Fix resolution
in SonarCloud, not a code change.

1 files changed, 21 insertions, 18 deletions

diff --git a/DomainDig/PortScanService.swift b/DomainDig/PortScanService.swift
index 1f3e649..808b38a 100644
--- a/DomainDig/PortScanService.swift
+++ b/DomainDig/PortScanService.swift
@@ -89,24 +89,7 @@ struct PortScanService {
                 switch state {
                 case .ready:
                     connection.receive(minimumIncompleteLength: 1, maximumLength: 256) { data, _, _, error in
-                        guard error == nil,
-                              let data,
-                              !data.isEmpty,
-                              let rawBanner = String(data: data, encoding: .utf8) else {
-                            context.finish(with: nil)
-                            return
-                        }
-
-                        let printableBanner = rawBanner.filter { character in
-                            guard let scalar = character.unicodeScalars.first,
-                                  character.unicodeScalars.count == 1 else {
-                                return false
-                            }
-                            return (32...126).contains(scalar.value)
-                        }
-
-                        let banner = String(printableBanner.prefix(80))
-                        context.finish(with: banner.isEmpty ? nil : banner)
+                        context.finish(with: printableBanner(from: data, error: error))
                     }
                 case .failed, .cancelled:
                     context.finish(with: nil)
@@ -123,6 +106,26 @@ struct PortScanService {
         }
     }
 
+    private static func printableBanner(from data: Data?, error: Error?) -> String? {
+        guard error == nil,
+              let data,
+              !data.isEmpty,
+              let rawBanner = String(data: data, encoding: .utf8) else {
+            return nil
+        }
+
+        let printable = rawBanner.filter { character in
+            guard let scalar = character.unicodeScalars.first,
+                  character.unicodeScalars.count == 1 else {
+                return false
+            }
+            return (32...126).contains(scalar.value)
+        }
+
+        let banner = String(printable.prefix(80))
+        return banner.isEmpty ? nil : banner
+    }
+
     private static func probe(domain: String, port: UInt16) async -> PortProbeResult {
         await probe(domain: domain, port: port, timeout: 1.5)
     }