feat: add evidence search and stabilize pdf previews

- add document evidence parsing/search/open routes, Hermes tool wiring, local index settings/status, and the document-evidence skill plus design notes
- fix PDF resource tabs by rendering PDFs inline with pdf.js canvases instead of iframe preview pages, release PDF documents on close, and document the fourth-PDF stall bug
- keep PDF preview at 2x rendering while removing the previous lazy-load/placeholder direction, and make dev:hot bind loopback defaults externally reachable

Verification:
- node --check rust/crates/mnote-web/browser/document-resource-tab-runtime.js
- node scripts/task-dev-hot-plan-test.js
- cargo test -p mnote-web --manifest-path rust/Cargo.toml pdf_preview_page_does_not_render_visible_toolbar
- cargo test -p mnote-web --manifest-path rust/Cargo.toml document_shell_returns_page_aggregate_snapshot
- cargo build -p mnote-web --manifest-path rust/Cargo.toml
- browser smoke: sequentially opened the four tea_seed_oil_cosmetic PDFs; fourth PDF rendered 15/15 canvases, iframeCount=0, browser errors=0

rust/crates/mnote-web/src/app.rs

@@ -158,7 +158,10 @@ impl AppState {
         let control_plane = Arc::new(open_control_plane_store());
         Self {
             config: Arc::new(config),
-            local_folder_watcher_registry: LocalFolderWatcherRegistry::new(buffer_store.clone()),
+            local_folder_watcher_registry: LocalFolderWatcherRegistry::new(
+                buffer_store.clone(),
+                control_plane.clone(),
+            ),
             editor_actor: actor,
             block_delta_tx,
             stream_delta_tx,
@@ -184,12 +187,12 @@ impl AppState {
 }
 
 #[cfg(test)]
-fn open_control_plane_store() -> SqliteControlPlaneStore {
+pub(crate) fn open_control_plane_store() -> SqliteControlPlaneStore {
     SqliteControlPlaneStore::in_memory().expect("初始化测试 SQLite 控制面")
 }
 
 #[cfg(not(test))]
-fn open_control_plane_store() -> SqliteControlPlaneStore {
+pub(crate) fn open_control_plane_store() -> SqliteControlPlaneStore {
     let db_path = env::var("MNOTE_CONTROL_PLANE_DB_PATH")
         .ok()
         .filter(|value| !value.trim().is_empty())