move v0.1 artifacts to DELETE/, fix xcode build, bump calver to 2026.03.14

- move backend/, clients/, scripts/ to DELETE/ (v0.1 era, replaced by on-device arch)
- delete feature/v0.1-backend-and-macos branch
- add TaskStore dependency to project.yml
- fix ComposeViewModel deinit concurrency, make toMessageSummary public
- regenerate Xcode project, verify macOS build succeeds

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

DELETE/clients/macos/MagnumOpusTests/APIClientTests.swift

@@ -0,0 +1,55 @@
+import Testing
+@testable import MagnumOpus
+
+@Suite("APIClient")
+struct APIClientTests {
+	@Test("decodes thread list from JSON")
+	func decodesThreadList() throws {
+		let json = """
+		{
+			"threads": [
+				{
+					"threadId": "t001",
+					"subject": "Q1 Planning",
+					"authors": "Alice, Bob",
+					"totalMessages": 3,
+					"tags": "inbox,unread",
+					"timestamp": 1709884532,
+					"accountId": "personal"
+				}
+			]
+		}
+		""".data(using: .utf8)!
+
+		let response = try JSONDecoder().decode(ThreadListResponse.self, from: json)
+		#expect(response.threads.count == 1)
+		#expect(response.threads[0].subject == "Q1 Planning")
+	}
+
+	@Test("decodes message list from JSON")
+	func decodesMessageList() throws {
+		let json = """
+		{
+			"messages": [
+				{
+					"messageId": "msg001@example.com",
+					"threadId": "t001",
+					"fromHeader": "Alice <alice@example.com>",
+					"toHeader": "user@example.com",
+					"subject": "Q1 Planning",
+					"date": "2024-03-08T10:15:32+01:00",
+					"inReplyTo": "",
+					"body": "Hey, let's plan Q1.",
+					"tags": "inbox,unread",
+					"timestamp": 1709884532,
+					"accountId": "personal"
+				}
+			]
+		}
+		""".data(using: .utf8)!
+
+		let response = try JSONDecoder().decode(MessageListResponse.self, from: json)
+		#expect(response.messages.count == 1)
+		#expect(response.messages[0].body == "Hey, let's plan Q1.")
+	}
+}