perf(sidebar): 保留兜底定位并限制全树查询频率

- 缓存节点连接期间按 1.5s safety-net 周期完整复核
- html style 变化时立即绕过 fast path 重新定位
- 覆盖流式热路径、定时复核、HMR 信号与节点替换行为

tests/center-column-locator.spec.ts

@@ -1,53 +1,103 @@
 // @vitest-environment jsdom
-import { afterEach, describe, expect, it, vi } from 'vitest'
-import { resolveCenterColumn } from '../src/client/center-column.ts'
+import { describe, expect, it, vi } from 'vitest'
+import {
+  CENTER_COLUMN_REVALIDATE_MS,
+  resolveCenterColumn,
+} from '../src/client/center-column.ts'
 
-afterEach(() => {
-  document.body.innerHTML = ''
-})
+interface Fixture {
+  doc: Document
+  col: HTMLDivElement
+  slot: HTMLDivElement
+}
 
-function connectedColumn(): { col: HTMLDivElement; slot: HTMLDivElement } {
-  const col = document.createElement('div')
-  const slot = document.createElement('div')
+function connectedColumn(doc = document.implementation.createHTMLDocument()): Fixture {
+  const col = doc.createElement('div')
+  const slot = doc.createElement('div')
   slot.dataset.slot = 'conversation'
   col.append(slot)
-  document.body.append(col)
-  return { col, slot }
+  doc.body.append(col)
+  return { doc, col, slot }
 }
 
 describe('center-column locator (issue #403)', () => {
-  it('reuses a connected cached column without querying the app tree', () => {
-    const { col } = connectedColumn()
-    const query = vi.fn<() => Element | null>(() => null)
+  it('reuses a connected cached column without querying during the hot-path window', () => {
+    const { doc, col, slot } = connectedColumn()
+    let now = 0
+    const query = vi.fn<() => Element | null>(() => slot)
+    const options = { document: doc, query, now: () => now }
 
-    expect(resolveCenterColumn(col, query)).toBe(col)
+    expect(resolveCenterColumn(col, options)).toBe(col)
+    now = CENTER_COLUMN_REVALIDATE_MS - 1
+    expect(resolveCenterColumn(col, options)).toBe(col)
     expect(query).not.toHaveBeenCalled()
   })
 
-  it('queries and adopts the replacement after the cached column detaches', () => {
-    const stale = connectedColumn().col
+  it('fully revalidates a connected cache at the 1.5s safety-net boundary', () => {
+    const { doc, col, slot } = connectedColumn()
+    let now = 0
+    const query = vi.fn<() => Element | null>(() => slot)
+    const options = { document: doc, query, now: () => now }
+
+    expect(resolveCenterColumn(col, options)).toBe(col)
+    expect(query).not.toHaveBeenCalled()
+
+    now = CENTER_COLUMN_REVALIDATE_MS
+    expect(resolveCenterColumn(col, options)).toBe(col)
+    expect(query).toHaveBeenCalledTimes(1)
+  })
+
+  it('revalidates immediately when the html style signal changes', () => {
+    const { doc, col, slot } = connectedColumn()
+    let now = 0
+    const query = vi.fn<() => Element | null>(() => slot)
+    const options = { document: doc, query, now: () => now }
+
+    expect(resolveCenterColumn(col, options)).toBe(col)
+    expect(query).not.toHaveBeenCalled()
+
+    doc.documentElement.style.setProperty('--dsh-sidebar-width', '320px')
+    now = 1
+    expect(resolveCenterColumn(col, options)).toBe(col)
+    expect(query).toHaveBeenCalledTimes(1)
+
+    // The same fingerprint is cheap again; one style change causes one full
+    // validation instead of turning later streaming mutations into queries.
+    now = 2
+    expect(resolveCenterColumn(col, options)).toBe(col)
+    expect(query).toHaveBeenCalledTimes(1)
+  })
+
+  it('queries and adopts the replacement as soon as the cached column detaches', () => {
+    const first = connectedColumn()
+    const stale = first.col
     stale.remove()
-    const { col: replacement, slot } = connectedColumn()
+    const { col: replacement, slot } = connectedColumn(first.doc)
     const query = vi.fn<() => Element | null>(() => slot)
 
-    expect(resolveCenterColumn(stale, query)).toBe(replacement)
+    expect(resolveCenterColumn(stale, { document: first.doc, query, now: () => 1 })).toBe(replacement)
     expect(query).toHaveBeenCalledTimes(1)
   })
 
   it('queries when no column has been cached yet', () => {
-    const { col, slot } = connectedColumn()
+    const { doc, col, slot } = connectedColumn()
     const query = vi.fn<() => Element | null>(() => slot)
 
-    expect(resolveCenterColumn(null, query)).toBe(col)
+    expect(resolveCenterColumn(null, { document: doc, query, now: () => 0 })).toBe(col)
     expect(query).toHaveBeenCalledTimes(1)
   })
 
   it('rejects a missing or detached query result', () => {
-    expect(resolveCenterColumn(null, () => null)).toBeUndefined()
+    const doc = document.implementation.createHTMLDocument()
+    expect(resolveCenterColumn(null, { document: doc, query: () => null, now: () => 0 })).toBeUndefined()
 
-    const detachedCol = document.createElement('div')
-    const detachedSlot = document.createElement('div')
+    const detachedCol = doc.createElement('div')
+    const detachedSlot = doc.createElement('div')
     detachedCol.append(detachedSlot)
-    expect(resolveCenterColumn(null, () => detachedSlot)).toBeUndefined()
+    expect(resolveCenterColumn(null, {
+      document: doc,
+      query: () => detachedSlot,
+      now: () => 1,
+    })).toBeUndefined()
   })
 })