Add personal data tools, 2nd Brain trust toggle, and research agents

Personal Data Tools: native Calendar, Reminders, Contacts (hidden pending
Apple TCC fix in beta), and Location & Maps access via EventKit, Contacts
framework, and MapKit. Write actions (create event/reminder, complete
reminder) gate through an approval sheet. Four hardened-runtime entitlements
added to oAI.entitlements; Info.plist usage strings added for all services.
Personal Data section shows a β badge while Contacts is hidden.

2nd Brain always-trust: inline toggle on the Agent Skills row for the skill
named "2nd Brain" skips the bash approval dialog when the command contains
.brain_helper.py, gated by three runtime checks in MCPService.

Research agents: spawn_research_agents tool runs up to 5 concurrent read-only
sub-agents (read_file, list_directory, search_files, web_search — no write,
no bash, no nesting). Bounded by maxConcurrentAgents setting (default 3) and
a hard ceiling of 8 tasks. Added items field to Tool.Function.Parameters.Property
for JSON Schema array support; wired into AnthropicProvider.convertParametersToDict.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

oAI/Providers/AIProvider.swift

@@ -229,6 +229,19 @@ struct Tool: Codable {
                 let type: String
                 let description: String
                 let `enum`: [String]?
+                let items: Items?
+
+                /// Item schema for `type: "array"` properties (e.g. an array of strings).
+                struct Items: Codable {
+                    let type: String
+                }
+
+                init(type: String, description: String, enum: [String]? = nil, items: Items? = nil) {
+                    self.type = type
+                    self.description = description
+                    self.enum = `enum`
+                    self.items = items
+                }
             }
         }
     }