feat(mcp): expose an OAuth-authenticated /mcp/oauth endpoint

Register Mcp::oauthRoutes() (RFC 8414/9728 discovery, RFC 7591 DCR, the
mcp:use Passport scope) and a second streamable-HTTP MCP endpoint at
/mcp/oauth guarded by auth:api, so OAuth clients (Claude Desktop/web,
ChatGPT) can connect without a static token. The existing Sanctum /mcp
endpoint is left untouched.

Tighten config/mcp.php redirect_domains to the Claude and ChatGPT hosted
callbacks only (no wildcard).

config/mcp.php

@@ -0,0 +1,55 @@
+<?php
+
+return [
+
+    /*
+    |--------------------------------------------------------------------------
+    | Redirect Domains
+    |--------------------------------------------------------------------------
+    |
+    | These domains are the domains that OAuth clients are permitted to use
+    | for redirect URIs. Each domain should be specified with its scheme
+    | and host. Domains not in this list will raise validation errors.
+    |
+    | An "*" may be used to allow all domains.
+    |
+    */
+
+    'redirect_domains' => [
+        // Anthropic's hosted callback for Claude Desktop / Claude web connectors.
+        'https://claude.ai',
+        // OpenAI's hosted callback for ChatGPT connectors.
+        'https://chatgpt.com',
+    ],
+
+    /*
+    |--------------------------------------------------------------------------
+    | Allowed Custom Schemes
+    |--------------------------------------------------------------------------
+    |
+    | Native desktop OAuth clients like Cursor and VS Code use private-use URI
+    | schemes (RFC 8252) for redirect callbacks instead of standard schemes
+    | like HTTPS. Here, you may list which custom schemes you will allow.
+    |
+    */
+
+    'custom_schemes' => [
+        // 'claude',
+        // 'cursor',
+        // 'vscode',
+    ],
+
+    /*
+    |--------------------------------------------------------------------------
+    | Authorization Server
+    |--------------------------------------------------------------------------
+    |
+    | Here you may configure the OAuth authorization server issuer identifier
+    | per RFC 8414. This value appears in your protected resource and auth
+    | server metadata endpoints. When null, this defaults to `url('/')`.
+    |
+    */
+
+    'authorization_server' => null,
+
+];

routes/ai.php

@@ -8,12 +8,29 @@ use Laravel\Mcp\Facades\Mcp;
 | MCP Routes
 |--------------------------------------------------------------------------
 |
-| Remote (streamable HTTP) MCP server. Authenticated with Sanctum personal
-| access tokens carrying an `mcp:read` ability, throttled per user. The
-| Pro-plan gate is enforced inside each tool so a lapsed subscription stops
-| working without the user having to revoke their token.
+| Remote (streamable HTTP) MCP server, exposed on two endpoints:
+|
+| - `/mcp` is authenticated with Sanctum personal access tokens carrying an
+|   `mcp:read` ability (Claude Code, static bearer token, read/read_write via
+|   abilities). Left completely unchanged.
+| - `/mcp/oauth` is authenticated with OAuth 2.1 (Authorization Code + PKCE)
+|   for clients that sign in rather than paste a token — Claude Desktop / web
+|   and ChatGPT connectors. `Mcp::oauthRoutes()` registers the RFC 8414 / 9728
+|   discovery endpoints, the RFC 7591 DCR endpoint and the `mcp:use` Passport
+|   scope; the package's AddWwwAuthenticateHeader middleware then turns an
+|   unauthenticated request into the mandatory 401 bootstrap challenge.
+|
+| OAuth connections carry only the single `mcp:use` scope, so `tokenCan`
+| reports no `mcp:write` ability and the write tools stay read-only for them
+| (see WriteTool). The Pro-plan gate is enforced inside each tool under either
+| guard, so a lapsed subscription stops working without revoking access.
 |
 */
 
+Mcp::oauthRoutes();
+
 Mcp::web('/mcp', WhisperMoneyServer::class)
     ->middleware(['auth:sanctum', 'abilities:mcp:read', 'throttle:60,1']);
+
+Mcp::web('/mcp/oauth', WhisperMoneyServer::class)
+    ->middleware(['auth:api', 'throttle:60,1']);