Some fixes to the live test suite (#32)

This PR contains the work done to fix the live test suite, which started failing once the Amiibo API began returning Switch 2 games, and tidies the test suite around it.

### Changes

- **Live tests:** replaced the assertion that the first amiibo has no Switch 2 games with a usage check, matching the other platforms. The live data now includes Switch 2 entries for most amiibos.
- **Live tests:** refreshed the minimum item counts and the earliest accepted last-updated date to the values observed in October 2026, and documented in the README how to refresh them.
- **All tests:** moved test descriptions from `@Test("...")` strings into backticked function names, and aligned every case on the same GIVEN/WHEN/THEN structure.
- **Live client:** replaced the TODO about DocC inherited docs with a note. The compiler does not inherit documentation for protocol witnesses, so the repeated doc comments stay on purpose.

Reviewed-on: #32
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>

Sources/AmiiboService/Public/Clients/AmiiboLiveClient.swift

@@ -54,7 +54,8 @@ public struct AmiiboLiveClient: Sendable {
 }
 
 // MARK: - AmiiboClient
-// TODO: Remove the documentation from the functions inside the following extension as the `--enable-inherited-docs` flag when generating DocC documentation is not working as intended (?).
+// NOTE: The `AmiiboClient` documentation is repeated below on purpose, as the compiler does not inherit
+// documentation for protocol witnesses and DocC would otherwise render these functions undocumented.
 
 extension AmiiboLiveClient: AmiiboClient {