feat(settings): add Blocks tab — 12-block decision schema reference

Read-only display of BLOCK_CONFIG from block_writer.py with CREAC role
and JWM functional-purpose annotations per block (sourced from
docs/block-schema.md).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web-ui/src/lib/api/settings.ts

@@ -169,3 +169,27 @@ export function useMcpRegistrations() {
     staleTime: 60_000,
   });
 }
+
+export type McpBlock = {
+  id: string;
+  index: number;
+  title: string;
+  gen_type: string;
+  model: string;
+  temperature: number | null;
+  max_tokens: number | null;
+  creac_role: string | null;
+  jwm_purpose: string | null;
+};
+
+export function useMcpBlocks() {
+  return useQuery({
+    queryKey: ["settings", "mcp-blocks"] as const,
+    queryFn: ({ signal }) =>
+      apiRequest<{ blocks: McpBlock[]; count: number }>(
+        "/api/settings/mcp/blocks",
+        { signal },
+      ),
+    staleTime: 5 * 60_000, // 5 minutes — static reference data
+  });
+}