feat(blog): prune posts removed or renamed upstream

the blog repo is the source of truth for the full set of posts, but
upserts alone never delete: removing a file or changing a slug or
filename left the old row serving forever. each poll now reconciles —
after upserting the current tree, events under source='blog' whose id
is not in the parsed set are deleted via a new EventWriter::prune_events
port. nothing is lost: git still has every post, and restoring or
fixing a file re-ingests it on the next tip change.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/moments-data/src/blog.rs

@@ -171,6 +171,18 @@ impl EventSource for BlogSource {
         }
 
         let total = self.writer.upsert_events(&events).await?;
+
+        // The repo is the source of truth for the full set of posts: anything
+        // stored under source='blog' that no longer parses out of the current
+        // tree (deleted file, renamed slug/filename, broken frontmatter) is
+        // pruned. Nothing is lost — git still has it, and fixing or restoring
+        // the file re-ingests it on the next tip change.
+        let keep: Vec<String> = events.iter().map(|e| e.id.clone()).collect();
+        let pruned = self.writer.prune_events(Source::Blog, &keep).await?;
+        if pruned > 0 {
+            tracing::info!(pruned, "blog posts removed upstream; pruned from store");
+        }
+
         self.state.save(SOURCE_NAME, Some(&tip), None).await?;
         debug!(ingested = total, tip = %tip, "blog poll complete");
         Ok(total)

crates/moments-data/src/lib.rs

@@ -479,6 +479,22 @@ impl EventWriter for PgStore {
         Ok(inserted)
     }
 
+    async fn prune_events(&self, source: Source, keep_ids: &[String]) -> Result<usize, StoreError> {
+        let n = sqlx::query(
+            r#"
+            DELETE FROM events
+            WHERE source = $1 AND NOT (id = ANY($2))
+            "#,
+        )
+        .bind(source.as_str())
+        .bind(keep_ids)
+        .execute(&self.pool)
+        .await
+        .map_err(map_err)?
+        .rows_affected();
+        Ok(n as usize)
+    }
+
     async fn upsert_repo_languages(&self, languages: &[RepoLanguage]) -> Result<usize, StoreError> {
         if languages.is_empty() {
             return Ok(0);