authorize returns 500 instead of a typed error when the auth method doesn't exist

What happens

POST /provider/:id/authorize returns a 500 when method doesn't resolve to a registered auth method.

ProviderAuth.authorize indexes into the hook table with no guard on either lookup (packages/opencode/src/provider/auth.ts:166):

const method = hooks[input.providerID].methods[input.method]
if (method.type !== "oauth") return

AuthorizeInput.method is Schema.Finite (auth.ts:57), so any finite number decodes, and the handler passes it straight through (server/routes/instance/httpapi/handlers/provider.ts:70-74). Two inputs make method undefined and the .type read throw:

• an index past the end of methods
• a providerID with no registered auth hook at all

A TypeError isn't one of the typed ProviderAuth.Errors the endpoint declares, so mapProviderAuthError never converts it and the client gets a 500 instead of a structured error.

Expected

A 400 with a typed error, the way callback already does 25 lines below for the same class of problem:

const match = pending.get(input.providerID)
if (!match) return yield* new OauthMissing({ providerID: input.providerID })

Repro

With the provider-oauth-parity plugin fixture from test/server/httpapi-provider.test.ts (it registers two methods, so index 2 is one past the end):

requestAuthorize({ providerID, method: 2, headers })   // 500, expected 400
requestAuthorize({ providerID: "no-such-provider", headers })  // 500, expected 400