Signals: index the judge's query, six calls at once, one call per item on the server's key, tokens counted, a week's look-back an admin sets, edits that ask again only what was picked out (#274, #275, #276)

The judge's query read all of entries (605 MB, 566 ms) on every wake; an
index on each feed's items by date, as the query asks, and the rechecks
in a half of their own. Calls ran one at a time, about 150 ms each, so a
new Signal's month of about 8,000 items took twenty minutes: six in flight
now. On the server's key everyone's Signals on an item share one call.
TypeSafe's token counts go to /metrics and each jev span.

An item's text is cut at 1,000 characters instead of 2,000: on 55 real
items of eight podcast feeds and six Signals, on the development key,
1,000 changed none of 330 verdicts (nor did the same request twice) and
saved 12% of the input tokens, 1,266 to 1,112 a call; 500 changed one.

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

web/CHANGELOG.md

@@ -14,10 +14,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Admin, Server: a setting to give everyone Signals on the server's TypeSafe key (#271).
+- Admin, Server: how many days back a new Signal reads (#276).
 
 ### Changed
 
 - Unless the server pays for them, Signals are turned on in Settings with your own TypeSafe key, and the Signals folder shows only once they are on (#271).
+- A Signal's dialog says how far back it reads, and that an edit reads again only what was picked out (#276).
 
 ## [1.1.0] - 2026-10-16