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/graph/state.py

@@ -105,6 +105,11 @@ class State(BaseModel):
     ] = None
 
     # ── Turn products (previous turn's decisions & results) ──────────────
+    execution_report: Annotated[
+        str | None,
+        "Executor's final answer, prepared before review; cleared on resumed execution",
+        take_last,
+    ] = None
     current_step_id: Annotated[str | None, "Current step ID from data engine", take_last] = None
     structured_decisions: Annotated[
         str | None,