chore: move legacy SDK e2e script into examples/

scripts/e2e_legacy_sdk.py becomes examples/demo_legacy_sdk.py to sit
alongside the other runnable demos (local/cloud/query-modes), and the
README's Runnable examples list now points at it. Docstring command
updated to the new path; the legacy script docstring also calls out
that it exercises the 0.2.x compatibility methods.

The scripts/ directory had no other entries and is removed.

examples/demo_legacy_sdk.py

@@ -0,0 +1,98 @@
+"""End-to-end smoke test of the legacy SDK compatibility layer against the real cloud API.
+
+Exercises the legacy `pageindex_sdk` 0.2.x methods preserved on `PageIndexClient`:
+submit_document, is_retrieval_ready, get_tree, get_document, chat_completions
+(sync + stream), and delete_document.
+
+Run: PAGEINDEX_API_KEY=... python examples/demo_legacy_sdk.py
+"""
+from __future__ import annotations
+import os
+import sys
+import time
+from pathlib import Path
+
+from dotenv import load_dotenv
+
+load_dotenv()
+
+from pageindex import PageIndexClient
+
+
+def log(step: str, detail: str = "") -> None:
+    print(f"[e2e] {step}" + (f" — {detail}" if detail else ""), flush=True)
+
+
+def main() -> int:
+    api_key = os.environ.get("PAGEINDEX_API_KEY")
+    if not api_key:
+        print("PAGEINDEX_API_KEY not set", file=sys.stderr)
+        return 1
+
+    pdf = Path("examples/documents/attention-residuals.pdf")
+    if not pdf.exists():
+        print(f"Test PDF missing: {pdf}", file=sys.stderr)
+        return 1
+
+    client = PageIndexClient(api_key=api_key)
+    log("init", f"cloud mode (key={api_key[:6]}…)")
+
+    # 1) submit_document (legacy SDK signature — fire-and-forget)
+    submit_resp = client.submit_document(file_path=str(pdf))
+    doc_id = submit_resp["doc_id"]
+    log("submit_document", f"doc_id={doc_id}")
+
+    try:
+        # 2) poll is_retrieval_ready (with hard timeout)
+        deadline = time.time() + 600  # 10 min
+        while time.time() < deadline:
+            if client.is_retrieval_ready(doc_id):
+                log("is_retrieval_ready", "True")
+                break
+            time.sleep(8)
+        else:
+            log("is_retrieval_ready", "TIMEOUT")
+            return 2
+
+        # 3) get_tree
+        tree = client.get_tree(doc_id)
+        node_count = len(tree.get("result") or tree.get("tree") or [])
+        log("get_tree", f"top-level nodes={node_count}, status={tree.get('status')}")
+
+        # 4) get_document (metadata)
+        meta = client.get_document(doc_id)
+        log("get_document", f"name={meta.get('name')!r} pages={meta.get('pageNum')} status={meta.get('status')}")
+
+        # 5) chat_completions (non-stream)
+        chat = client.chat_completions(
+            messages=[{"role": "user", "content": "What is this paper about? Answer in one sentence."}],
+            doc_id=doc_id,
+        )
+        answer = (chat.get("choices") or [{}])[0].get("message", {}).get("content", "")
+        log("chat_completions", f"answer={answer[:120]!r}")
+
+        # 6) chat_completions (stream) — full consumption
+        log("chat_completions stream", "starting…")
+        print("[stream] ", end="", flush=True)
+        chunk_count = 0
+        for chunk in client.chat_completions(
+            messages=[{"role": "user", "content": "List 3 keywords from this paper."}],
+            doc_id=doc_id,
+            stream=True,
+        ):
+            print(chunk, end="", flush=True)
+            chunk_count += 1
+        print()  # newline after streaming
+        log("chat_completions stream", f"chunks received={chunk_count}")
+
+    finally:
+        # 7) delete_document
+        del_resp = client.delete_document(doc_id)
+        log("delete_document", f"resp={del_resp}")
+
+    log("done", "all steps OK")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())