fix: limit resource preview watches to active tab

Root cause: every local resource preview tab kept its own /api/local-folder/events EventSource alive. Hidden PDF and Office tabs consumed browser same-origin connection slots, so later preview iframes/file reads stalled and rendered as blank pages.

Changes:
- keep passive resource file watching active-tab only
- close inactive resource-tab EventSources on tab activation and release
- update the bug record with the PDF fifth-open and XLSX fourth-open repro and verification

Verification:
- node --check rust/crates/mnote-web/browser/document-resource-tab-runtime.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: opened 5 XLSX previews; #4 and #5 completed with tableCount=1
- browser smoke: opened 5 DHA PDFs; #5 rendered 8/8 canvases, iframeCount=0, browser errors=0

bugs/05-editor-mainline/done/2026-06-04-pdf-resource-tab-fourth-open-stall.md

@@ -1,19 +1,21 @@
-# PDF resource tab 连续打开第 4 个文件卡住
+# resource tab 连续打开多个预览后卡住
 
 ## 现象
 
 - 在文档页 resource tab 内连续打开多个 PDF 时，第 4 个 PDF 必现卡住。
 - 卡住时 tab 标题已经切换，但 iframe 仍停在 `about:blank` 或空 body，PDF canvas 数量为 0。
 - 单独打开 `/pdf-preview` 页面、或独立页面中复用单个 iframe 连续切换 PDF，均不能复现。
+- PDF 改成 tab 内 canvas 渲染后，第 4 个 PDF 可打开，但继续打开第 5 个仍会卡住；表格预览第 4 个仍会卡住。
 
 ## 根因
 
-PDF resource tab 通过 iframe 加载 `/pdf-preview`，连续创建/替换 PDF iframe 后会进入空白加载状态。问题不在具体 PDF 文件，也不在页数懒加载策略。
+根因不是具体 PDF 文件，也不是页数懒加载策略，而是 resource tab 为每个本地资源预览都常驻一个 `/api/local-folder/events` EventSource。连续打开多个 PDF / Office 预览后，隐藏 tab 的 EventSource 仍占用浏览器同源连接槽，新的 Office iframe 或 PDF 文件读取请求会被排队，表现为空白预览。
 
 ## 修复
 
 - resource tab 内的 PDF 改为直接使用 pdf.js 渲染 canvas，不再通过 iframe 打开 `/pdf-preview`。
 - 关闭或替换 PDF resource tab 时销毁 pdf.js document，释放渲染资源。
+- resource tab 的本地文件监听改为 active-only：只保留当前激活资源 tab 的 EventSource，切换 tab 或回到页面 tab 时关闭其它资源 tab 的监听。
 - 移除 `/pdf-preview` 内此前排查用的懒加载、占位页和多页预渲染逻辑，保留 2x 起步渲染清晰度。
 - `dev:hot` 默认把 loopback bind 修正为 `0.0.0.0:<port>`，避免外网访问不到 3000。
 
@@ -25,6 +27,8 @@ PDF resource tab 通过 iframe 加载 `/pdf-preview`，连续创建/替换 PDF i
   - `literature/Ouyang_2024_Frontiers_aged_Camellia_oleifera_oil_AD.pdf`
   - `literature/Leclere_2025_OCL_Tea_oil_concentrate.pdf`
 - 第 4 个 PDF 结果：`canvasCount=15`，`iframeCount=0`，`status=15 / 15`，浏览器错误 0。
+- 真实浏览器连续打开 5 个 DHA PDF，第 5 个 `Sun2022_DHA_Maillard_Kinetics.pdf` 结果：`canvasCount=8`，`status=8 / 8`，浏览器错误 0。
+- 真实浏览器连续打开 5 个 XLSX 预览，第 4/5 个均 `status=完成`，`tableCount=1`，浏览器错误 0。
 - `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`

rust/crates/mnote-web/browser/document-resource-tab-runtime.js

@@ -708,6 +708,7 @@ export const createResourceTabRuntime = (dependencies = {}) => {
     if (!activeEntry && window.__mnoteIntendedSlashRoot instanceof HTMLElement) window.__mnoteIntendedSlashRoot = null;
     if (role === 'primary') syncActiveResourceFileTreeRow(activeResource);
     syncActiveResourceUrlState(activeResource, role);
+    syncActivePassiveResourceWatch(role, activeResource);
     syncOpenEditorsSnapshot();
   };
 
@@ -898,12 +899,7 @@ export const createResourceTabRuntime = (dependencies = {}) => {
       }
       entry.mindmapRuntime = null;
     }
-    if (entry.resourceWatchEventSource) {
-      try {
-        entry.resourceWatchEventSource.close();
-      } catch (_) {}
-      entry.resourceWatchEventSource = null;
-    }
+    closePassiveResourceWatch(entry);
     if (entry.panel instanceof HTMLElement) entry.panel.replaceChildren();
   };
 
@@ -1092,11 +1088,40 @@ export const createResourceTabRuntime = (dependencies = {}) => {
     }
   };
 
+  const closePassiveResourceWatch = (entry) => {
+    if (!entry?.resourceWatchEventSource) return;
+    try {
+      entry.resourceWatchEventSource.close();
+    } catch (_) {}
+    entry.resourceWatchEventSource = null;
+    if (entry.panel instanceof HTMLElement) entry.panel.removeAttribute('data-mnote-resource-watch-ready');
+  };
+
+  const isActiveResourceTabEntry = (entry) => {
+    if (!(entry?.panel instanceof HTMLElement)) return false;
+    if (entry.panel.hidden === false) return true;
+    return entry.tab instanceof HTMLElement && entry.tab.getAttribute('aria-selected') === 'true';
+  };
+
+  const closeInactivePassiveResourceWatches = (activeEntry) => {
+    const role = normalizePaneRole(activeEntry?.paneRole || 'primary');
+    resourceTabRegistry.forEach((entry) => {
+      if (entry === activeEntry) return;
+      if (normalizePaneRole(entry?.paneRole) !== role) return;
+      closePassiveResourceWatch(entry);
+    });
+  };
+
   const installPassiveResourceWatch = (entry) => {
     if (!entry || entry.session || typeof window.EventSource !== 'function') return;
     const rootUri = String(entry.rootUri || '').trim();
     const path = String(entry.path || '').trim();
     if (!rootUri || !path) return;
+    if (!isActiveResourceTabEntry(entry)) {
+      closePassiveResourceWatch(entry);
+      return;
+    }
+    closeInactivePassiveResourceWatches(entry);
     if (entry.resourceWatchEventSource) {
       try {
         entry.resourceWatchEventSource.close();
@@ -1130,6 +1155,17 @@ export const createResourceTabRuntime = (dependencies = {}) => {
     });
   };
 
+  const syncActivePassiveResourceWatch = (paneRole, activeResource) => {
+    const activeEntry = activeResource ? resourceTabRegistry.get(activeResource) : null;
+    if (!activeEntry) {
+      resourceTabRegistry.forEach((entry) => {
+        if (normalizePaneRole(entry?.paneRole) === normalizePaneRole(paneRole)) closePassiveResourceWatch(entry);
+      });
+      return;
+    }
+    installPassiveResourceWatch(activeEntry);
+  };
+
   const releaseInlinePdfResource = (entry) => {
     if (!entry) return;
     const pdf = entry.inlinePdfDocument;