Rebuild: the live tail

coordinator:run plans the articles after each group's last range every
TAIL_EVERY_SECONDS (120): one LIST ACTIVE per name prefix gives every
group's newest article, and new articles become ranges at priority -1,
leased and prefetched before any history. A group gets a tail range once
it has TAIL_MIN_ARTICLES (100k, a chunk) new or its last planning is
TAIL_MAX_DELAY_MINUTES (15) ago, so quiet groups don't make a range every
round. History (planAll, hourly) is now only for groups not planned yet.
ranges:plan --tail plans one round.

Found on the way: with XFEATURE COMPRESS GZIP on, Eweka compresses LIST
ACTIVE's reply too ("215 NewsGroups Follow [COMPRESS=GZIP]"), and
listActive waited for a plain end that never came (groups:add --top too).
It reads the compressed reply now; the fake server in the test does both.

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

start/env.ts

@@ -47,6 +47,9 @@ export default await Env.create(new URL('../', import.meta.url), {
 
   // Coordinator
   RANGE_ARTICLES: Env.schema.number.optional(),
+  TAIL_EVERY_SECONDS: Env.schema.number.optional(),
+  TAIL_MIN_ARTICLES: Env.schema.number.optional(),
+  TAIL_MAX_DELAY_MINUTES: Env.schema.number.optional(),
   CHUNK_ARTICLES: Env.schema.number.optional(),
   LEASE_TTL_SECONDS: Env.schema.number.optional(),
   SPOOL_DIR: Env.schema.string.optional(),