fix: add compaction headroom for memory writes

src/agents/pi-settings.ts

@@ -0,0 +1,27 @@
+export const DEFAULT_PI_COMPACTION_RESERVE_TOKENS_FLOOR = 20_000;
+
+type PiSettingsManagerLike = {
+  getCompactionReserveTokens: () => number;
+  applyOverrides: (overrides: {
+    compaction: { reserveTokens: number };
+  }) => void;
+};
+
+export function ensurePiCompactionReserveTokens(params: {
+  settingsManager: PiSettingsManagerLike;
+  minReserveTokens?: number;
+}): { didOverride: boolean; reserveTokens: number } {
+  const minReserveTokens =
+    params.minReserveTokens ?? DEFAULT_PI_COMPACTION_RESERVE_TOKENS_FLOOR;
+  const current = params.settingsManager.getCompactionReserveTokens();
+
+  if (current >= minReserveTokens) {
+    return { didOverride: false, reserveTokens: current };
+  }
+
+  params.settingsManager.applyOverrides({
+    compaction: { reserveTokens: minReserveTokens },
+  });
+
+  return { didOverride: true, reserveTokens: minReserveTokens };
+}