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/Internal/Extensions/DateFormatter+Properties.swift

@@ -18,13 +18,11 @@ extension DateFormatter {
     
     // MARK: Properties
     
-    /// An ISO date formatter.
-    ///
-    /// This formatter implements the `yyyy-MM-dd` date format.
+    /// An ISO date formatter for the `yyyy-MM-dd` format.
     static let isoDate: DateFormatter = {
         let formatter = DateFormatter()
         
-        // A fixed-format date requires the POSIX locale, as the user's locale or 12/24-hour setting could otherwise alter the parsing.
+        // The POSIX locale keeps the user's locale and 12/24-hour setting from altering fixed-format parsing.
         formatter.locale = .init(identifier: "en_US_POSIX")
         formatter.dateFormat = "yyyy-MM-dd"
         formatter.timeZone = .init(secondsFromGMT: 0)
@@ -32,14 +30,13 @@ extension DateFormatter {
         return formatter
     }()
     
-    /// An ISO timestamp formatter.
+    /// An ISO timestamp formatter for the `yyyy-MM-dd'T'HH:mm:ss.SSSSSS` format.
     ///
-    /// This formatter implements the `yyyy-MM-dd'T'HH:mm:ss.SSSSSS` custom date format.
-    /// Within the context of this library, this formatter is solely used to decode a date formatted as a timestamp that is returned by the ``AmiiboService/getLastUpdated()`` function.
+    /// Used only to decode the timestamp returned by ``AmiiboService/getLastUpdated()``.
     static let isoTimestamp: DateFormatter = {
         let formatter = DateFormatter()
         
-        // A fixed-format date requires the POSIX locale, as the user's locale or 12/24-hour setting could otherwise alter the parsing.
+        // The POSIX locale keeps the user's locale and 12/24-hour setting from altering fixed-format parsing.
         formatter.locale = .init(identifier: "en_US_POSIX")
         formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSSSS"
         formatter.timeZone = .init(secondsFromGMT: 0)