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/archive-entry.ts

@@ -0,0 +1,17 @@
+import { Archiver, EntryData } from "archiver";
+import { Readable } from "stream";
+/** Allow only one active entry; compression and the response provide backpressure. */
+export function appendArchiveEntry(archive: Archiver, source: Readable, options: EntryData): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const cleanup = () => {
+      archive.removeListener("entry", done); archive.removeListener("error", fail);
+      archive.removeListener("close", closed); source.removeListener("error", fail);
+    };
+    const done = () => { cleanup(); resolve(); };
+    const fail = (error: Error) => { cleanup(); source.destroy(); reject(error); };
+    const closed = () => fail(new Error("archive_cancelled"));
+    archive.once("entry", done); archive.once("error", fail); archive.once("close", closed);
+    source.once("error", fail);
+    archive.append(source, options);
+  });
+}