feat(server): add Opus 4.7 to claude provider with xhigh effort

Adds claude-opus-4-7 and claude-opus-4-7[1m] alongside the existing 4.6
entries (4.6 stays default). Opus 4.7 introduces a new "xhigh" effort
level between high and max; the option only surfaces on 4.7 models.

The SDK 0.2.71 effort union doesn't yet include xhigh, so the value is
cast at the assignment site.

packages/cli/tests/15-provider.test.ts

@@ -31,6 +31,16 @@ type ProviderModel = {
 };
 
 const EXPECTED_CLAUDE_MODELS = [
+  {
+    id: "claude-opus-4-7[1m]",
+    model: "Opus 4.7 1M",
+    descriptionFragment: "1M context window",
+  },
+  {
+    id: "claude-opus-4-7",
+    model: "Opus 4.7",
+    descriptionFragment: "Latest release",
+  },
   {
     id: "claude-opus-4-6[1m]",
     model: "Opus 4.6 1M",