Scaffold octosentry MVP: unified GitHub security alert feed0.1.0

MenuBarExtra popover aggregating Dependabot, code scanning, and secret
scanning alerts for a single repo into one severity-ranked stream. Swift 6
strict concurrency, zero third-party dependencies, PAT-via-env-var auth as
a dev-only shortcut ahead of the device authorization flow.

1 files changed, 52 insertions, 0 deletions

diff --git a/octosentry/SeverityMapping.swift b/octosentry/SeverityMapping.swift
new file mode 100644
index 0000000..5befb46
--- /dev/null
+++ b/octosentry/SeverityMapping.swift
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+//
+//  SeverityMapping.swift
+//  octosentry
+//
+//  Normalizes each GitHub alert source's native severity vocabulary into
+//  the shared SecurityEventSeverity scale. Kept as a single auditable
+//  source file per the spec (§4) rather than scattered across the client.
+//
+
+import Foundation
+
+nonisolated enum SeverityMapping {
+    /// Dependabot alerts report CVSS-derived severity on the vulnerability object.
+    static func dependabot(_ nativeSeverity: String) -> SecurityEventSeverity {
+        switch nativeSeverity.lowercased() {
+        case "critical": .critical
+        case "high": .high
+        case "moderate", "medium": .medium
+        case "low": .low
+        default: .medium
+        }
+    }
+
+    /// Code scanning alerts expose `rule.security_severity_level` (CVSS-derived) when
+    /// present, falling back to `rule.severity` (note/warning/error) otherwise.
+    static func codeScanning(securitySeverityLevel: String?, ruleSeverity: String?) -> SecurityEventSeverity {
+        if let securitySeverityLevel {
+            switch securitySeverityLevel.lowercased() {
+            case "critical": return .critical
+            case "high": return .high
+            case "medium": return .medium
+            case "low": return .low
+            default: break
+            }
+        }
+        switch ruleSeverity?.lowercased() {
+        case "error": return .high
+        case "warning": return .medium
+        case "note": return .low
+        default: return .medium
+        }
+    }
+
+    /// Secret scanning has no native severity field. Per spec: validated/active
+    /// secrets are treated as critical, unvalidated ones as high.
+    static func secretScanning(validity: String?) -> SecurityEventSeverity {
+        switch validity?.lowercased() {
+        case "active": .critical
+        default: .high
+        }
+    }
+}