Rebuild: the coordinator spools replies without inflating them

On homelab (1 Gbit, 20 connections, ~630k articles/s) the coordinator
used 1.3-1.7 cores, mostly GC of the text it inflated only to know a
compressed reply was complete, plus a copy of every reply. A raw reply
is now complete when it ends in ".\r\n" (no copy): 0.4-0.5 cores at
the same rate.

".\r\n" can also end a network read inside the compressed data (~1 in
16M reads, a few dozen times over the whole target). Such a chunk
doesn't inflate on the worker: it reports it (POST ranges/:id/corrupt),
the spooled chunk is removed and the range goes back to the queue; the
prefetcher fetches it again. The rest of that reply breaks the
connection's next command, so the connection is replaced.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

start/routes.ts

@@ -51,6 +51,7 @@ router
         router.post('ranges/:id/heartbeat', [controllers.Node, 'heartbeat'])
         router.post('ranges/:id/finish', [controllers.Node, 'finish'])
         router.post('ranges/:id/release', [controllers.Node, 'release'])
+        router.post('ranges/:id/corrupt', [controllers.Node, 'corrupt'])
       })
       .prefix('node')
       .as('node')