OAuth logout throws an exception

# Bug report ## Details When attempting to logout with an OAuth authenticated session an exception is thrown. ### Describe the bug An exception is thrown when calling `agent.Logout()` when authenticated via OAuth. ``` Unhandled exception: idunno.AtProto.LogoutException: Exception of type 'idunno.AtProto.LogoutException' was thrown. at idunno.AtProto.AtProtoAgent.Logout(CancellationToken cancellationToken) in G:\idunno.Bluesky\src\idunno.AtProto\Authentication\AtProtoAgent.cs:line 817 at Samples.ConsoleShellOAuth.Program.PerformOperations(String loginHandle, Uri proxyUri, CancellationToken cancellationToken) in G:\idunno.Bluesky\samples\Samples.ConsoleShellOAuth\Program.cs:line 126 at Samples.ConsoleShellOAuth.Program.PerformOperations(String loginHandle, Uri proxyUri, CancellationToken cancellationToken) in G:\idunno.Bluesky\samples\Samples.ConsoleShellOAuth\Program.cs:line 126 at System.CommandLine.Command.<>c__DisplayClass32_0.<<SetAction>b__0>d.MoveNext() --- End of stack trace from previous location --- at System.CommandLine.Invocation.InvocationPipeline.InvokeAsync(ParseResult parseResult, CancellationToken cancellationToken) ``` The revoke endpoint, https://bsky.social/oauth/revoke, responds with HTTP/2 401 date: Sun, 28 Sep 2025 14:48:11 GMT content-type: application/json x-powered-by: Express access-control-allow-origin: * access-control-max-age: 86400 access-control-allow-methods: * access-control-allow-headers: Content-Type,DPoP cache-control: no-store pragma: no-cache dpop-nonce: W08iptlWQlzIZ_rzk37XAIdLhNT7fJpch7T2sdZVSTc access-control-expose-headers: DPoP-Nonce access-control-expose-headers: WWW-Authenticate www-authenticate: DPoP algs="RS256 RS384 RS512 PS256 PS384 PS512 ES256 ES256K ES384 ES512", error="invalid_dpop_proof" vary: Accept-Encoding {"error":"invalid_dpop_proof","error_description":"DPoP \"ath\" claim not allowed"} ### Expected behavior No exception is thrown and the refresh token, then the access token are revoked. ## Helpful Extra information ### What operating system(s) are you using? - [X] Windows - [ ] macOS - [ ] Ubuntu - [ ] Other Linux - [ ] Other (specify below)