feat: add official Codex skill and harden task execution

Install and update artemis-use with task diagnostics and plugin guidance. Preserve cross-device file receipts, review canonical reports, guard stage transitions and reduce small history summaries. Improve exploration lifecycle, request recovery and browser live connections.

artemis/exploration/report.py

@@ -0,0 +1,47 @@
+"""Persist and deliver the executor's answer before independent final review."""
+
+import hashlib
+import json
+from pathlib import Path
+from uuid import uuid4
+
+
+def save_execution_report(ctx, report: str) -> dict:
+    from artemis.exploration.store import explorations
+
+    directory = Path(ctx.data_engine.base_dir)
+    notes = directory / "notes"
+    notes.mkdir(parents=True, exist_ok=True)
+    # The regular report readers use output.md and result.json. Write complete
+    # replacements so a concurrent reader cannot observe half a report.
+    for path, content in (
+        (notes / "output.md", report),
+        (directory / "result.json", json.dumps({"result": report}, ensure_ascii=False)),
+    ):
+        temporary = path.with_name(f".{path.name}.{uuid4().hex}.tmp")
+        try:
+            temporary.write_text(content, encoding="utf-8")
+            temporary.replace(path)
+        finally:
+            temporary.unlink(missing_ok=True)
+
+    # Keep the entire answer despite the conversation's per-message size limit.
+    # A repeated settlement of the same answer must not duplicate its delivery.
+    digest = hashlib.sha256(report.encode("utf-8")).hexdigest()
+    sequences = []
+    for offset in range(0, len(report), 10000):
+        message = explorations.add_message(
+            ctx.exploration_id,
+            report[offset : offset + 10000],
+            f"report:{ctx.exploration_run_id}:{digest}:{offset}",
+            role="assistant",
+            source="exploration",
+            metadata={"run_id": ctx.exploration_run_id, "kind": "execution_report"},
+        )
+        sequences.append(message["sequence"])
+    return {
+        "report_path": "notes/output.md",
+        "result_path": "result.json",
+        "content_sha256": digest,
+        "exploration_message_sequences": sequences,
+    }