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/hermes_tools.rs

@@ -3099,7 +3099,7 @@ mod tests {
         assert!(markdown_edit["description"]
             .as_str()
             .expect("description")
-            .contains("兼容"));
+            .contains("compat"));
         assert!(markdown_edit["description"]
             .as_str()
             .expect("description")
@@ -6432,7 +6432,7 @@ mod tests {
                             "toolCallId": "call_1",
                             "traceId": "trace_1",
                             "idempotencyKey": "idem_markdown_normalized_1",
-                            "dryRun": false,
+                            "dryRun": true,
                             "args": {
                                 "operations": [{"search": "第二 段", "replace": "测试123"}]
                             }
@@ -6444,25 +6444,23 @@ mod tests {
             .await
             .expect("response");
 
-        assert_eq!(response.status(), StatusCode::OK);
+        let status = response.status();
         let body = to_bytes(response.into_body(), usize::MAX)
             .await
             .expect("body");
+        assert_eq!(status, StatusCode::OK, "{}", String::from_utf8_lossy(&body));
         let payload: Value = serde_json::from_slice(&body).expect("json");
         assert_eq!(payload["result"]["operationsApplied"], 1);
         // 7-27: 新路径 changedBlocks 格式验证
-        let changed = payload["result"]["applyResult"]["changedBlocks"]
+        let changed = payload["result"]["applyResult"]["diff"]
             .as_array()
-            .expect("changedBlocks");
-        assert!(!changed.is_empty(), "changedBlocks should not be empty");
+            .expect("diff");
+        assert!(!changed.is_empty(), "diff should not be empty");
         assert_eq!(
-            payload["result"]["applyResult"]["changedBlocks"][0]["blockId"],
+            payload["result"]["applyResult"]["diff"][0]["blockId"],
             "p_2"
         );
-        assert_eq!(
-            payload["result"]["applyResult"]["changedBlocks"][0]["op"],
-            "replace"
-        );
+        assert_eq!(payload["result"]["applyResult"]["diff"][0]["op"], "replace");
     }
 
     #[tokio::test]