Add local CLI access via Unix-socket server

New CLIServerService listens on a Unix domain socket
(~/Library/Application Support/oAI/cli.sock) speaking a minimal
HTTP/1.1 subset, for one-shot non-streaming shell access to a single
fixed model — e.g. an `ai "prompt"` zsh function — without opening
the app window and without going through the tool-calling loop.

Configured in Settings > MCP > CLI Access (toggle, provider, model —
deliberately independent of the chat UI's active model). JSON
request/response envelope rather than raw text so new fields (model
override, streaming, tool support) can be added later without a
breaking wire-format change.

Verified live end-to-end against a real OpenRouter request, error
paths, and clean-shutdown socket cleanup. 10 new unit tests cover
the HTTP framing/parsing logic.

oAI/Services/SettingsService.swift

@@ -1043,6 +1043,36 @@ class SettingsService {
         }
     }
 
+    // MARK: - CLI Server
+
+    /// Local Unix-socket server (CLIServerService) for one-shot, non-streaming shell access to a
+    /// single fixed model — deliberately separate from the chat UI's defaultProvider/defaultModel
+    /// so switching models in the GUI never changes shell-tool behavior, same reasoning as the
+    /// email handler's own dedicated provider/model pair above.
+    var cliServerEnabled: Bool {
+        get { cache["cliServerEnabled"] == "true" }
+        set {
+            cache["cliServerEnabled"] = String(newValue)
+            DatabaseService.shared.setSetting(key: "cliServerEnabled", value: String(newValue))
+        }
+    }
+
+    var cliServerProvider: String {
+        get { cache["cliServerProvider"] ?? "openrouter" }
+        set {
+            cache["cliServerProvider"] = newValue
+            DatabaseService.shared.setSetting(key: "cliServerProvider", value: newValue)
+        }
+    }
+
+    var cliServerModel: String {
+        get { cache["cliServerModel"] ?? "" }
+        set {
+            cache["cliServerModel"] = newValue
+            DatabaseService.shared.setSetting(key: "cliServerModel", value: newValue)
+        }
+    }
+
     var emailSubjectIdentifier: String {
         get { cache["emailSubjectIdentifier"] ?? "[OAIBOT]" }
         set {