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, 3 insertions, 3 deletions

diff --git a/DomainDig/HistoryView.swift b/DomainDig/HistoryView.swift
index 316fcce..5350168 100644
--- a/DomainDig/HistoryView.swift
+++ b/DomainDig/HistoryView.swift
@@ -115,7 +115,7 @@ struct HistoryView: View {
             Button("Clear All", role: .destructive) {
                 viewModel.clearHistory()
             }
-            Button("Cancel", role: .cancel) {}
+            Button("Cancel", role: .cancel) { /* Dismiss only; SwiftUI closes the alert. */ }
         } message: {
             Text("This will delete all saved history entries. This cannot be undone.")
         }
@@ -314,7 +314,7 @@ struct HistoryDetailView: View {
                     isCloudflareProxied: snapshot.httpHeaders.contains(where: { $0.name.lowercased() == "cf-ray" }),
                     customPortsExpanded: .constant(false),
                     customPortInput: .constant(""),
-                    onScanCustomPorts: {}
+                    onScanCustomPorts: { /* Historical snapshot; re-scanning is not offered here. */ }
                 )
                 .padding(.top, appDensity.metrics.sectionSpacing)
             }
@@ -344,7 +344,7 @@ struct HistoryDetailView: View {
             Button("Run with Snapshot Resolver") {
                 viewModel.rerunLookup(from: entry, useSnapshotResolver: true)
             }
-            Button("Cancel", role: .cancel) {}
+            Button("Cancel", role: .cancel) { /* Dismiss only; SwiftUI closes the alert. */ }
         } message: {
             Text(viewModel.resolverMismatchNote(for: entry) ?? "Choose how to reproduce this snapshot.")
         }