feat(codebuddy-cn): add API key auth + credit quota tracker

Two additions on top of the merged CodeBuddy CN OAuth provider:

1. API key auth — connect with a direct API key (sent as
   Authorization: Bearer), not only via OAuth device-code flow.
   - registry: add authModes ["oauth","apikey"] + hasOAuth; combined Bearer
     auth already forwards the key, token-refresh skips key connections.
   - providers POST: accept dual-auth providers (authModes includes
     "apikey") that live under category "oauth" — previously rejected as
     "Invalid provider". Also fixes the same latent gap for xai.

2. Quota tracker — surface CodeBuddy CN credit balance on the usage
   dashboard for both OAuth and API-key connections.
   - registry: add transport.usage.url (Tencent billing endpoint) +
     features.usage/usageApikey so the connection is quota-eligible.
   - new CN-scoped handler services/usage/codebuddy-cn.js: POST the billing
     meter endpoint, unwrap data.Response.Data.Accounts[]. The payload mixes
     two credit types that must not be merged:
       * refill/base ("基础体验包") — recurring allowance; cycle resets well
         before the resource expires (CycleEndTime << DeductionEndTime).
         Reads the *Cycle* balance, resetAt = next refresh. Cadence-labelled.
       * bonus ("活动赠送包") — one-shot credits that expire at CycleEndTime.
         Reads the plain Capacity balance. Labelled "Bonus Pack N".
     One quota row per package, soonest-expiring first.
   - register handler under "codebuddy-cn" in USAGE_HANDLERS.

Frontend needs no change — USAGE_SUPPORTED_PROVIDERS/USAGE_APIKEY_PROVIDERS
and the generic parseQuotaData branch already cover this shape.

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/providers/registry/codebuddy-cn.js

@@ -16,6 +16,8 @@ export default {
     },
   },
   category: "oauth",
+  authModes: ["oauth", "apikey"],
+  hasOAuth: true,
   transport: {
     baseUrl: "https://copilot.tencent.com/v2/chat/completions",
     forceStream: true,
@@ -36,6 +38,11 @@ export default {
       header: "Authorization",
       scheme: "bearer",
     },
+    // Quota endpoint differs from the chat gateway: POST returns nested Tencent
+    // billing payload (data.Response.Data.Accounts[]). See services/usage/codebuddy-cn.js.
+    usage: {
+      url: "https://copilot.tencent.com/v2/billing/meter/get-user-resource",
+    },
   },
   models: [
     { id: "glm-5.2", name: "GLM-5.2" },
@@ -63,4 +70,8 @@ export default {
     platform: "CLI",
     pollInterval: 5000,
   },
+  features: {
+    usage: true,
+    usageApikey: true,
+  },
 };