fix: give the notification home a place to live in the owner's database

/sethome answered "no such table: config" from every surface. ChatHub is
owner-bound, so its pool is a {userid}.db, and `config` is a registry
table that only exists in system.db — the write had no table to land in.

The visible half was the lesser one. The notification consumer resolves
the home source before it delivers anything, and on an error it dropped
the batch: every `notify` from a background agent and every cron-job
completion has been discarded, silently, for as long as the hub has been
per-user. That error path now degrades to the default home instead — a
batch that got that far is data nobody can recreate, and the destination
is the one thing there with a sane fallback.

Where the setting belongs was never in doubt: one member choosing
Telegram must not move anybody else's notifications, so it is owner
state and it goes in their own file. The new owner table is `user_config`
and it deliberately does not reuse the registry name. The two hold
different namespaces — instance settings the admin owns versus one
person's own preferences — and a table called `config` in both files
would have turned this exact mistake into a silent read of the other
scope, which is strictly worse than the loud failure that revealed it.

Additive, so no migration: open_user_pool re-applies the owner schema on
every unlock, and the table appears at each user's next login.

crates/skald-core/src/chat_hub/mod.rs

@@ -15,7 +15,7 @@ use inbox::{ConversationInbox, QueuedMessage, build_unit, drain_leading_user};
 
 use crate::approval::ApprovalManager;
 use crate::cron::TaskManager;
-use crate::db::{chat_history, chat_llm_tools, chat_sessions, chat_sessions_stack, config, sources};
+use crate::db::{chat_history, chat_llm_tools, chat_sessions, chat_sessions_stack, sources, user_config};
 use crate::events::{GlobalEvent, ServerEvent};
 use crate::notification::Notification;
 use crate::session::handler::{
@@ -434,15 +434,23 @@ impl ChatHub {
     }
 
     /// Set which source is the "home" for background agent notifications.
+    ///
+    /// The hub is owner-bound, so `self.db` is that person's own database and the
+    /// home is theirs: one member choosing Telegram cannot move anybody else's
+    /// notifications. That is why the key lives in the owner table `user_config`
+    /// and not in the registry `config` one — which this used to write, against a
+    /// `{userid}.db` that has no such table, so `/sethome` only ever answered
+    /// "no such table: config" and every notification batch was dropped by the
+    /// consumer below.
     pub async fn set_home(&self, source_id: &str) -> anyhow::Result<()> {
-        config::set(&self.db, HOME_SOURCE_KEY, source_id).await?;
+        user_config::set(&self.db, HOME_SOURCE_KEY, source_id).await?;
         info!(source_id, "ChatHub: home source set");
         Ok(())
     }
 
     /// Returns the current home source id, falling back to `web` if not configured.
     pub async fn home_source(&self) -> anyhow::Result<String> {
-        Ok(config::get(&self.db, HOME_SOURCE_KEY)
+        Ok(user_config::get(&self.db, HOME_SOURCE_KEY)
             .await?
             .unwrap_or_else(|| DEFAULT_HOME_SOURCE.to_string()))
     }
@@ -978,9 +986,18 @@ impl ChatHub {
                 None    => break, // ChatHub dropped
             };
 
+            // A batch that got this far is data nobody can recreate, and the
+            // destination is the one thing here with a sane default — so a failed
+            // read degrades to it instead of discarding the notifications (which
+            // is precisely what a missing `config` table did, silently, to every
+            // `notify` and every cron completion on the box).
             let home = match hub.home_source().await {
                 Ok(h)  => h,
-                Err(e) => { error!(error = %e, "notification consumer: home_source failed"); continue; }
+                Err(e) => {
+                    error!(error = %e, fallback = DEFAULT_HOME_SOURCE,
+                           "notification consumer: home_source failed");
+                    DEFAULT_HOME_SOURCE.to_string()
+                }
             };
 
             let count = notes.len();