Few fixes and improvements to the library, plus Github Actions setup (#31)

This PR contains the work done to fix a cancellation-mapping bug in `AmiiboLiveClient`, bring the client under offline test coverage, add the conformances SwiftUI and persistence need, and moves CI and documentation publishing to GitHub Actions. All public API changes are additive.

### Fix

- `AmiiboLiveClient` reported an early task cancellation as `.unknown("CancellationError()")`. The OpenAPI runtime wraps every error in `ClientError`, so the `CancellationError` check never matched; it now also checks the wrapped error and throws `.cancelled`.

### Tests

- `ThrowingTransport` and `StubTransport` test doubles let the live client run offline. New tests cover error mapping, HTTP status → error mapping, `oneOf` object-vs-list decoding, `"amiibo": null`, sorting, filter → query encoding, `Platform`/`Release` mapping, and the date transcoder.
- Models gained `package` memberwise initializers so tests can build real fixtures without `@testable`. These are not public API.
- The test target now depends on `OpenAPIRuntime` and `HTTPTypes` (both already in the dependency graph).

### API
- Models are `Codable` and `Identifiable` (`Amiibo.id` is its `identifier`; the key/name models use `key`).
- Filters are `Hashable`.

### Documentation
- Doc comments trimmed library-wide; one repeated `- Throws:` sentence appeared 24 times. `Library.md` and the README tightened to match.

### CI and docs publishing
- `ci.yml`: build and offline tests on PRs and pushes to `main`.
- `live-tests.yml`: weekly and on-demand run against the live API.
- `docs.yml`: builds DocC on PRs, deploys to GitHub Pages on `main`. Pinned to Xcode 26 because swift-docc-plugin 1.5.0 fails to launch its tools under Xcode 27.
- The generated `docs/` folder (327 files) is removed from the repository and ignored.

Reviewed-on: #31
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>

Tests/AmiiboService/Helpers/Transports/StubTransport.swift

@@ -0,0 +1,72 @@
+// ===----------------------------------------------------------------------===
+//
+// This source file is part of the Amiibo Service open source project
+//
+// Copyright (c) 2026 Röck+Cöde VoF. and the Amiibo Service project authors
+// Licensed under Apache license v2.0
+//
+// See LICENSE for license information
+// See CONTRIBUTORS for the list of Amiibo Service project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// ===----------------------------------------------------------------------===
+
+import Foundation
+import HTTPTypes
+import OpenAPIRuntime
+
+/// A transport that answers every request with a canned response, for testing purposes.
+struct StubTransport: ClientTransport {
+
+    // MARK: Type aliases
+
+    /// A closure that builds the response for a request.
+    typealias Handler = @Sendable (HTTPRequest) throws -> (HTTPResponse, HTTPBody?)
+
+    // MARK: Properties
+
+    /// The handler that builds the response.
+    private let handler: Handler
+
+    // MARK: Initializers
+
+    /// Initializes this transport with a response handler.
+    init(handler: @escaping Handler) {
+        self.handler = handler
+    }
+
+    /// Initializes this transport with a fixed response.
+    init(status: HTTPResponse.Status, json: String? = nil) {
+        self.init { _ in
+            Self.response(status: status, json: json)
+        }
+    }
+
+    // MARK: Functions
+
+    func send(
+        _ request: HTTPRequest,
+        body: HTTPBody?,
+        baseURL: URL,
+        operationID: String
+    ) async throws -> (HTTPResponse, HTTPBody?) {
+        try handler(request)
+    }
+
+    /// Builds a response with a status and an optional JSON body.
+    static func response(
+        status: HTTPResponse.Status,
+        json: String? = nil
+    ) -> (HTTPResponse, HTTPBody?) {
+        guard let json else {
+            return (.init(status: status), nil)
+        }
+
+        return (
+            .init(status: status, headerFields: [.contentType: "application/json"]),
+            .init(json)
+        )
+    }
+
+}