perf: bound request work and resource usage (#866)

* perf: bound request work and resource usage

* fix: address performance review regressions

* fix: guard content expiration and dashboard state

* fix: tolerate cache outages and retire derived paths

* fix: revalidate expiration claims and status pagination

* fix: retry interrupted repository metadata cleanup

* fix: retire obsolete content cache storage

* fix: activate tree metadata and recheck expiration claims

* fix: fence cache publication across expiration

* fix: recover staged trees and enforce cache lifecycle cleanup

* fix: prune expired transforms during database outages

* fix: finish conference removals and reload expiration candidates

src/core/response-stream.ts

@@ -0,0 +1,24 @@
+import { Readable, Writable } from "stream";
+
+/** Cancel upstream on every response terminal event, including a pre-header close. */
+export function streamResponse(source: Readable, response: Writable,
+  onError: (error: Error) => void): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const cleanup = () => {
+      response.removeListener("close", done);
+      response.removeListener("finish", done);
+      response.removeListener("error", failed);
+      source.removeListener("error", upstreamFailed);
+      source.unpipe(response);
+      source.destroy();
+    };
+    const done = () => { cleanup(); resolve(); };
+    const failed = (error: Error) => { cleanup(); reject(error); };
+    const upstreamFailed = (error: Error) => { onError(error); done(); };
+    response.once("close", done);
+    response.once("finish", done);
+    response.once("error", failed);
+    source.once("error", upstreamFailed);
+    if (response.destroyed || response.writableEnded) done(); else source.pipe(response);
+  });
+}