Refactor: Relocate SDK files to lib and update imports

Moved all SDK files from the `sdk` directory to the `lib` directory to better align with project structure. Updated all associated import paths across the codebase to reflect this change. Removed unused or commented-out code in `SiteCoordinator.js` for better clarity and maintainability.

workers/site/lib/handleStreamData.ts

@@ -0,0 +1,104 @@
+interface StreamChoice {
+  index?: number;
+  delta: {
+    content: string;
+  };
+  logprobs: null;
+  finish_reason: string | null;
+}
+
+interface StreamResponse {
+  type: string;
+  data: {
+    choices?: StreamChoice[];
+    delta?: {
+      text?: string;
+    };
+    type?: string;
+    content_block?: {
+      type: string;
+      text: string;
+    };
+  };
+}
+
+const handleStreamData = (
+  controller: ReadableStreamDefaultController,
+  encoder: TextEncoder,
+) => {
+  return (
+    data: StreamResponse,
+    transformFn?: (data: StreamResponse) => StreamResponse,
+  ) => {
+    if (!data?.type || data.type !== "chat") {
+      return;
+    }
+
+    let transformedData: StreamResponse;
+
+    if (transformFn) {
+      transformedData = transformFn(data);
+    } else {
+      if (
+        data.data.type === "content_block_start" &&
+        data.data.content_block?.type === "text"
+      ) {
+        transformedData = {
+          type: "chat",
+          data: {
+            choices: [
+              {
+                delta: {
+                  content: data.data.content_block.text || "",
+                },
+                logprobs: null,
+                finish_reason: null,
+              },
+            ],
+          },
+        };
+      } else if (data.data.delta?.text) {
+        transformedData = {
+          type: "chat",
+          data: {
+            choices: [
+              {
+                delta: {
+                  content: data.data.delta.text,
+                },
+                logprobs: null,
+                finish_reason: null,
+              },
+            ],
+          },
+        };
+      } else if (data.data.choices?.[0]?.delta?.content) {
+        transformedData = {
+          type: "chat",
+          data: {
+            choices: [
+              {
+                index: data.data.choices[0].index,
+                delta: {
+                  content: data.data.choices[0].delta.content,
+                },
+                logprobs: null,
+                finish_reason: data.data.choices[0].finish_reason,
+              },
+            ],
+          },
+        };
+      } else if (data.data.choices) {
+        transformedData = data;
+      } else {
+        return;
+      }
+    }
+
+    controller.enqueue(
+      encoder.encode(`data: ${JSON.stringify(transformedData)}\n\n`),
+    );
+  };
+};
+
+export default handleStreamData;