ADR-0022 stage 8d: schema cache refresh wiring

New `AppEvent::SchemaCacheRefreshed(SchemaCache)` event +
App handler that stores it on `app.schema_cache`.

Runtime helper `refresh_schema_cache(database, event_tx)`
fetches table / column / relationship names via the
`list_names_for` worker request (added in stage 7) and posts
the assembled cache. Wired into every site that already
posts `TablesRefreshed`:
  - `seed_initial_tables` (initial project load).
  - Project-switch path in `handle_project_switch`.
  - `RebuildSucceeded` path.
  - Post-DDL path (`spawn_command`).
  - Post-replay path.

Result: schema-aware identifier completion (added in 8c)
becomes live — Tab on `show data ` offers the actual table
names from the current project, `drop column from T: ` (or
similar) offers existing columns, etc. The cache stays
fresh across DDL and rebuild without per-keystroke worker
round-trips (one refresh per schema-mutating action is
amortised across many subsequent keystrokes).

Best-effort: a failed `list_names_for` for any individual
slot kind leaves that field empty in the cache rather than
suppressing the whole refresh — partial completion beats
no completion.

Tests: 738 passing, 0 failing, 1 ignored (unchanged
total — this stage is wiring, not new test surface; the
synthetic-cache tests from stage 8c remain the regression
net for the completion logic itself). Clippy clean.

src/runtime.rs

@@ -466,6 +466,7 @@ async fn handle_project_switch(
             if let Ok(tables) = session.database().list_tables().await {
                 let _ = event_tx.send(AppEvent::TablesRefreshed(tables)).await;
             }
+            refresh_schema_cache(session.database(), event_tx).await;
         }
         Err(e) => {
             let _ = event_tx
@@ -817,6 +818,36 @@ async fn seed_initial_tables(database: &Database, event_tx: &mpsc::Sender<AppEve
             error!(error = %e, "failed to seed initial table list");
         }
     }
+    refresh_schema_cache(database, event_tx).await;
+}
+
+/// Fetch the three identifier lists (tables / columns /
+/// relationships) and post them as `SchemaCacheRefreshed`
+/// (ADR-0022 §9 + stage 8d). Always sends an event, even on
+/// partial failure — best-effort completion is better than
+/// no completion. Called wherever `TablesRefreshed` is sent
+/// today; the schema cache lives on the App and feeds Tab
+/// completion for identifier slots.
+async fn refresh_schema_cache(
+    database: &Database,
+    event_tx: &mpsc::Sender<AppEvent>,
+) {
+    use crate::completion::SchemaCache;
+    use crate::dsl::ident_slot::IdentSlot;
+    let mut cache = SchemaCache::default();
+    if let Ok(tables) = database.list_names_for(IdentSlot::TableName).await {
+        cache.tables = tables;
+    }
+    if let Ok(columns) = database.list_names_for(IdentSlot::Column).await {
+        cache.columns = columns;
+    }
+    if let Ok(rels) = database
+        .list_names_for(IdentSlot::RelationshipName)
+        .await
+    {
+        cache.relationships = rels;
+    }
+    let _ = event_tx.send(AppEvent::SchemaCacheRefreshed(cache)).await;
 }
 
 /// Read `project.yaml` + `data/` to compute the rebuild
@@ -905,6 +936,7 @@ fn spawn_rebuild(
                 if let Ok(tables) = database.list_tables().await {
                     let _ = event_tx.send(AppEvent::TablesRefreshed(tables)).await;
                 }
+                refresh_schema_cache(&database, &event_tx).await;
             }
             Err(DbError::PersistenceFatal {
                 operation,
@@ -1003,6 +1035,9 @@ fn spawn_dsl_dispatch(
             }
             Err(e) => warn!(error = %e, "post-list_tables failed"),
         }
+        // Refresh the schema cache feeding Tab completion
+        // (ADR-0022 §9). Same timing as TablesRefreshed.
+        refresh_schema_cache(&database, &event_tx).await;
     });
 }
 
@@ -1337,6 +1372,7 @@ fn spawn_replay(
             }
             Err(e) => warn!(error = %e, "post-replay list_tables failed"),
         }
+        refresh_schema_cache(&database, &event_tx).await;
     });
 }