feat(rag): harden post-LightRAG runtime

Retire legacy OCR/media/evidence fallbacks, add local-folder event bus and Page Aggregate guards, and archive completed design checklists.

Validation: cargo test -p mnote-web -- --test-threads=1; cargo test --workspace -- --test-threads=1; git diff --check; codegraph sync .; codegraph_status.

rust/crates/mnote-web/src/routes/evidence.rs

@@ -1087,7 +1087,7 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn evidence_search_route_prefers_sqlite_index() {
+    async fn evidence_search_route_returns_retired_guard() {
         let root = std::env::temp_dir().join(format!(
             "mnote-evidence-route-sqlite-{}-{}",
             std::process::id(),
@@ -1182,22 +1182,15 @@ mod tests {
             .await
             .expect("response");
 
-        assert_eq!(response.status(), StatusCode::OK);
+        assert_eq!(response.status(), StatusCode::GONE);
         let body = to_bytes(response.into_body(), usize::MAX)
             .await
             .expect("body");
         let payload: Value = serde_json::from_slice(&body).expect("json");
-        let first = payload["results"]
-            .as_array()
-            .and_then(|items| items.first())
-            .expect("sqlite evidence result");
+        assert_eq!(payload["ok"], false);
         assert_eq!(
-            first["source"]["ownerDocumentPath"].as_str(),
-            Some("README.md")
-        );
-        assert_eq!(
-            first["source"]["schema"].as_str(),
-            Some("mnote.evidence_locator.v1")
+            payload["code"].as_str(),
+            Some("mnote_evidence_search_retired")
         );
         fs::remove_dir_all(&root).ok();
     }