fix: finalize durable Pi lifecycle

backend/src/runtime/maintenance-gate.ts

@@ -10,17 +10,25 @@ import {
 } from "node:fs";
 import { dirname } from "node:path";
 
+export interface MaintenanceDurability {
+  syncDirectory(directory: string): void;
+}
+
 /** A durable admission barrier. A lease spans the complete create/resume decision. */
 export class MaintenanceBarrier {
   private active: boolean;
   private admissions = 0;
   private waiters: (() => void)[] = [];
 
-  constructor(private readonly markerFile?: string) {
+  constructor(
+    private readonly markerFile?: string,
+    private readonly durability: MaintenanceDurability = defaultDurability,
+  ) {
     this.active = markerFile === undefined ? false : existsSync(markerFile);
   }
 
   acquire(): (() => void) | undefined {
+    this.reconcileActive();
     if (this.active) return undefined;
     this.admissions += 1;
     let released = false;
@@ -33,17 +41,44 @@ export class MaintenanceBarrier {
   }
 
   async activate(): Promise<void> {
-    this.persistMarker();
-    this.active = true;
-    if (this.admissions === 0) return;
-    await new Promise<void>((resolve) => this.waiters.push(resolve));
+    let persistError: unknown;
+    if (this.markerFile === undefined) {
+      this.active = true;
+    } else {
+      try {
+        this.persistMarker();
+      } catch (error) {
+        persistError = error;
+      } finally {
+        this.reconcileActive();
+      }
+    }
+    if (!this.active) throw persistError;
+    if (this.admissions > 0) {
+      await new Promise<void>((resolve) => this.waiters.push(resolve));
+    }
+    if (persistError !== undefined) throw persistError;
   }
 
   deactivate(): void {
-    this.removeMarker();
-    this.active = false;
+    if (this.markerFile === undefined) {
+      this.active = false;
+      return;
+    }
+    try {
+      this.removeMarker();
+    } finally {
+      this.reconcileActive();
+    }
+  }
+  status(): { active: boolean; admissions: number } {
+    this.reconcileActive();
+    return { active: this.active, admissions: this.admissions };
+  }
+
+  private reconcileActive(): void {
+    if (this.markerFile !== undefined) this.active = existsSync(this.markerFile);
   }
-  status(): { active: boolean; admissions: number } { return { active: this.active, admissions: this.admissions }; }
 
   private persistMarker(): void {
     if (!this.markerFile) return;
@@ -59,7 +94,7 @@ export class MaintenanceBarrier {
     }
     try {
       renameSync(temporary, this.markerFile);
-      syncDirectory(directory);
+      this.durability.syncDirectory(directory);
     } catch (error) {
       try { unlinkSync(temporary); } catch { /* already renamed or best-effort cleanup */ }
       throw error;
@@ -69,12 +104,14 @@ export class MaintenanceBarrier {
   private removeMarker(): void {
     if (!this.markerFile || !existsSync(this.markerFile)) return;
     unlinkSync(this.markerFile);
-    syncDirectory(dirname(this.markerFile));
+    this.durability.syncDirectory(dirname(this.markerFile));
   }
 }
 
-function syncDirectory(directory: string): void {
-  if (process.platform === "win32") return;
-  const fd = openSync(directory, "r");
-  try { fsyncSync(fd); } finally { closeSync(fd); }
-}
+const defaultDurability: MaintenanceDurability = {
+  syncDirectory(directory: string): void {
+    if (process.platform === "win32") return;
+    const fd = openSync(directory, "r");
+    try { fsyncSync(fd); } finally { closeSync(fd); }
+  },
+};