fix(gateway): capture config hash after plugin auto-enable to prevent restart loop

The startup internal-write hash was only recorded when auth-token
generation or control-UI origin seeding persisted changes, missing the
earlier plugin auto-enable write performed inside
loadGatewayStartupConfigSnapshot().  When chokidar detected the
auto-enable write the hash guard had nothing to compare against, so it
proceeded with a full config reload that triggered SIGUSR1, restarting
the gateway in a 3-6 minute loop that corrupted manifest.db mid-write.

Always read the final config hash after all startup writes complete so
the reloader can suppress the self-induced reload.

src/gateway/config-reload.test.ts

@@ -620,6 +620,34 @@ describe("startGatewayConfigReloader", () => {
 
     await harness.reloader.stop();
   });
+
+  it("does not dedupe when initialInternalWriteHash is null (#67436)", async () => {
+    const readSnapshot = vi
+      .fn<() => Promise<ConfigFileSnapshot>>()
+      .mockResolvedValueOnce(
+        makeSnapshot({
+          config: {
+            gateway: { reload: { debounceMs: 0 }, auth: { mode: "token", token: "startup" } },
+          },
+          hash: "startup-internal-1",
+        }),
+      );
+    const harness = createReloaderHarness(readSnapshot, {
+      initialInternalWriteHash: null,
+    });
+
+    harness.watcher.emit("change");
+    await vi.runOnlyPendingTimersAsync();
+
+    expect(readSnapshot).toHaveBeenCalledTimes(1);
+    // With a null hash the guard is a no-op, so the reload proceeds and
+    // detects a config diff → restart.  This is the pre-fix regression
+    // scenario from #67436 where plugin auto-enable was the only startup
+    // writer and the hash was never captured.
+    expect(harness.onRestart).toHaveBeenCalledTimes(1);
+
+    await harness.reloader.stop();
+  });
 });
 
 describe("shouldInvalidateSkillsSnapshotForPaths", () => {

src/gateway/server.impl.ts

@@ -284,7 +284,14 @@ export async function startGatewayServer(
         log,
       });
   cfgAtStart = controlUiSeed.config;
-  if (authBootstrap.persistedGeneratedToken || controlUiSeed.persistedAllowedOriginsSeed) {
+  // Always capture the final config hash after all startup writes (plugin
+  // auto-enable, auth token generation, control-UI origin seeding) so the
+  // config reloader can recognize its own startup writes and suppress the
+  // spurious hot-reload that would otherwise trigger a SIGUSR1 restart loop.
+  // Previously the hash was only captured when auth or control-UI persisted
+  // changes, missing the plugin auto-enable write performed earlier inside
+  // loadGatewayStartupConfigSnapshot().  See #67436.
+  {
     const startupSnapshot = await readConfigFileSnapshot();
     startupInternalWriteHash = startupSnapshot.hash ?? null;
   }