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, 41 insertions, 0 deletions

diff --git a/octosentry/GitHubAPIError.swift b/octosentry/GitHubAPIError.swift
new file mode 100644
index 0000000..7baf918
--- /dev/null
+++ b/octosentry/GitHubAPIError.swift
@@ -0,0 +1,41 @@
+//
+//  GitHubAPIError.swift
+//  octosentry
+//
+
+import Foundation
+
+enum GitHubAPIError: Error, LocalizedError, Sendable {
+    case missingToken
+    case network(String)
+    case invalidResponse
+    case unauthorized
+    case forbidden
+    case notFound
+    case rateLimited
+    case httpError(status: Int)
+    case decodingFailed(String)
+
+    var errorDescription: String? {
+        switch self {
+        case .missingToken:
+            "No GitHub token found in the GITHUB_TOKEN environment variable."
+        case .network(let message):
+            "Network error: \(message)"
+        case .invalidResponse:
+            "Received an unexpected response from GitHub."
+        case .unauthorized:
+            "GitHub rejected the token (401 Unauthorized)."
+        case .forbidden:
+            "Token lacks permission for this alert type (403 Forbidden)."
+        case .notFound:
+            "Repository or endpoint not found (404)."
+        case .rateLimited:
+            "GitHub API rate limit exceeded (429)."
+        case .httpError(let status):
+            "GitHub API returned HTTP \(status)."
+        case .decodingFailed(let message):
+            "Failed to parse GitHub API response: \(message)"
+        }
+    }
+}