rework web server so multiple clients can be server at a time

tests/test_session_runtime.py

@@ -0,0 +1,72 @@
+from __future__ import annotations
+
+import threading
+from pathlib import Path
+
+import pytest
+
+from backend.execution_context import active_node, emit_warning, execution_callbacks
+from backend.session_runtime import (
+    ensure_session_runtime_dirs,
+    resolve_client_path,
+    server_path_to_client_path,
+    session_upload_uri,
+)
+
+
+def test_session_paths_round_trip(monkeypatch, tmp_path):
+    monkeypatch.setenv("ARGONODE_APPDATA", str(tmp_path / "appdata"))
+
+    session_id = "session-test-1234"
+    input_dir, _ = ensure_session_runtime_dirs(session_id)
+    target = input_dir / "picked-folder" / "image.png"
+    target.parent.mkdir(parents=True, exist_ok=True)
+    target.write_bytes(b"png")
+
+    client_path = session_upload_uri("picked-folder/image.png")
+    resolved = resolve_client_path(client_path, session_id=session_id, allow_local_filesystem=False)
+
+    assert resolved == target.resolve()
+    assert server_path_to_client_path(target, session_id) == client_path
+
+
+def test_browser_sessions_cannot_escape_workspace(monkeypatch, tmp_path):
+    monkeypatch.setenv("ARGONODE_APPDATA", str(tmp_path / "appdata"))
+
+    session_id = "session-test-5678"
+    ensure_session_runtime_dirs(session_id)
+
+    outside_path = (tmp_path / "outside" / "secret.dat").resolve()
+
+    with pytest.raises(PermissionError):
+        resolve_client_path(str(outside_path), session_id=session_id, allow_local_filesystem=False)
+
+
+def test_execution_callbacks_are_thread_local():
+    results = []
+    lock = threading.Lock()
+    barrier = threading.Barrier(2)
+
+    def worker(label: str):
+        def on_warning(node_id: str, message: str):
+            with lock:
+                results.append((label, node_id, message))
+
+        with execution_callbacks(warning=on_warning):
+            with active_node(f"node-{label}"):
+                barrier.wait(timeout=5)
+                emit_warning(f"warning-{label}")
+
+    threads = [
+        threading.Thread(target=worker, args=("a",)),
+        threading.Thread(target=worker, args=("b",)),
+    ]
+    for thread in threads:
+        thread.start()
+    for thread in threads:
+        thread.join(timeout=5)
+
+    assert sorted(results) == [
+        ("a", "node-a", "warning-a"),
+        ("b", "node-b", "warning-b"),
+    ]