Signals: feeds made from your subscriptions, picked by Jev (#254)

A Signal is a name and keywords. A task beside DeadAir's asks TypeSafe's Jev, on the owner's own
key, about each item of their subscribed feeds from the last 30 days and every new one: one call
an item, one noul question for each of their Signals still to hear about it, 0.5 or more a fit.
Every verdict is kept, fitting or not, in signal_verdicts, so nothing is asked twice, and new
keywords drop a Signal's verdicts to be judged afresh. A key TypeSafe refuses (401/402/403) is
passed over until its owner saves another, so a bad key is not sent the whole queue.

A Signal's items come through entries_where with an EXISTS on its hits, so filters, search, sort
and read state are an ordinary list's, and reading an item in a Signal reads it in its feed.

The page shows Signals under the places, with New signal, and Settings takes the TypeSafe key,
which is never sent back. The browser suite stubs Jev in the fixture server (IPX_TYPESAFE_URL).

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

docs/architecture.md

@@ -41,6 +41,7 @@ id, and Caddy's request lines theirs. ipx also serves Prometheus metrics (`[web]
 | `crates/ipx/src/logbuf.rs` | Ring buffer behind the UI's Log view | — |
 | `crates/ipx/src/directory.rs` | Asking the directory service, and sharing this server's public feeds with it | — |
 | `crates/ipx/src/metrics.rs` | `/metrics` for Prometheus | — |
+| `crates/ipx/src/signals.rs` | Signals: asks Jev, on each person's TypeSafe key, which of their items fit their Signals | — |
 | `crates/directory/src/lib.rs` | The directory's HTTP API, its token check, the refresher | — |
 | `crates/directory/src/store.rs` | The directory's database: feeds, snapshots, blocked | — |
 | `crates/directory/src/config.rs` | The directory's config file: its tokens and their access | — |
@@ -96,8 +97,17 @@ subscriptions  user_id, feed_id, keywords, auto_download, allow_explicit,
                max_new_per_check                         PK (user_id, feed_id)
 entry_state    user_id, feed_id, guid, read, flagged, position
                                                          PK (user_id, feed_id, guid)
+signals        id, user_id, name, keywords
+signal_verdicts  signal_id, feed_id, guid, hit           PK (signal_id, feed_id, guid)
 ```
 
+A Signal (#254) is a feed someone makes from their own subscriptions. `signals::run`, a task of its
+own beside DeadAir's, woken by a scan with something new or a Signal made or changed, asks Jev
+about each item of the last 30 days that has no verdict yet for one of its owner's Signals: one
+call an item, a noul question a Signal, on the owner's `users.typesafe_key`. Every answer is kept,
+fitting or not, so nothing is asked twice; new keywords drop the Signal's verdicts. A Signal's
+items are `entries_where` with an `EXISTS` on its hits, so read state is the item's own.
+
 Read state is `entry_state` alone. `entries` had `read`, `flagged` and `position` columns from
 before accounts; two bugs came from queries still reading them, and they were dropped in 0.5.