feat(orchestration): nightly runner, rollover budgets, incremental checkpoints

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016DvdRZkyCy9NJpHYDdPqmS

orchestration/checkpoint.py

@@ -0,0 +1,32 @@
+"""Incremental, crash-safe JSON output. Each agent's output is (over)written atomically
+after every research round and again at finalize, so a hang or power loss mid-run still
+leaves the best-so-far result on disk under state/output/<trade_date>/<persona>.json.
+"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+from agents.schemas import AgentOutput, RunManifest
+
+
+def _atomic_write(path: Path, text: str) -> None:
+    tmp = path.with_suffix(path.suffix + ".tmp")
+    tmp.write_text(text)
+    os.replace(tmp, path)  # atomic on the same filesystem
+
+
+class Checkpointer:
+    def __init__(self, output_dir: Path, trade_date: str):
+        self.dir = Path(output_dir) / trade_date
+        self.dir.mkdir(parents=True, exist_ok=True)
+
+    def agent_path(self, persona_id: str) -> Path:
+        return self.dir / f"{persona_id}.json"
+
+    def write(self, output: AgentOutput) -> None:
+        _atomic_write(self.agent_path(output.persona_id), output.model_dump_json(indent=2))
+
+    def write_manifest(self, manifest: RunManifest) -> None:
+        _atomic_write(self.dir / "_manifest.json", manifest.model_dump_json(indent=2))