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>

Sources/AmiiboService/Public/Models/Amiibo/Amiibo+Platform.swift

@@ -13,8 +13,8 @@
 // ===----------------------------------------------------------------------===
 
 extension Amiibo {
-    /// A model that represents a collection of `Switch`, `Switch 2`, `3DS`, and `Wii U` games related to an amiibo.
-    public struct Platform: Sendable, Hashable {
+    /// A model that groups the games related to an amiibo by platform.
+    public struct Platform: Sendable, Hashable, Codable {
         
         // MARK: Properties
         
@@ -31,8 +31,21 @@ extension Amiibo {
         public let wiiU: [Game]
         
         // MARK: Initializers
-        
+
         /// Initializes this model.
+        package init(
+            `switch`: [Game] = [],
+            switch2: [Game] = [],
+            threeDS: [Game] = [],
+            wiiU: [Game] = []
+        ) {
+            self.switch = `switch`
+            self.switch2 = switch2
+            self.threeDS = threeDS
+            self.wiiU = wiiU
+        }
+
+        /// Initializes this model from the given payloads.
         ///
         /// > important: In case no data is provided, then an instance of this model is not created.
         ///