fix: restore the jump-to-bottom glide and keep user state, selections and scroll anchors in windowed lists

Pause scroll writes while the jump-to-bottom smooth scroll runs; keep rows with pending questions, approvals, recent interactions and selection ends mounted; cache Mermaid results; copy text spanning unmounted rows; anchor the sidebar on id changes; disable native overflow-anchor for windowed lists; write terminal output on the leading edge and before clear; forward remote events every 16 ms; flush streaming text before copy/export; add performance principle P10 (no UX regressions).

src/main/remote-event-batcher.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, it, vi } from 'vitest'
-import { RemoteEventBatcher } from './remote-event-batcher'
+import { REMOTE_EVENT_BATCH_FLUSH_INTERVAL_MS, RemoteEventBatcher } from './remote-event-batcher'
 
 const provenance = (eventIndex: number) => ({
   source: 'remote-semantic-transcript' as const,
@@ -46,6 +46,49 @@ describe('RemoteEventBatcher', () => {
     batcher.dispose()
   })
 
+  it('commits (and so forwards) streamed events within one frame by default', () => {
+    vi.useFakeTimers()
+    expect(REMOTE_EVENT_BATCH_FLUSH_INTERVAL_MS).toBe(16)
+    const persist = vi.fn((entries: readonly unknown[]) => entries.map(() => true))
+    const committed: string[] = []
+    const batcher = new RemoteEventBatcher<string>({ persist })
+    batcher.add(provenance(0), 'a', (event) => committed.push(event))
+    batcher.add(provenance(1), 'b', (event) => committed.push(event))
+    vi.advanceTimersByTime(15)
+    // Nothing is forwarded before it is persisted.
+    expect(committed).toEqual([])
+    vi.advanceTimersByTime(1)
+    expect(persist).toHaveBeenCalledOnce()
+    expect(committed).toEqual(['a', 'b'])
+    batcher.dispose()
+  })
+
+  it('reports a timer flush after its events committed, and not after a failed one', () => {
+    vi.useFakeTimers()
+    const order: string[] = []
+    let fail = false
+    const batcher = new RemoteEventBatcher<string>({
+      persist: (entries) => {
+        if (fail) throw new Error('disk full')
+        return entries.map(() => true)
+      },
+      onTimerFlushed: () => order.push('flushed'),
+      onError: () => order.push('error')
+    })
+    batcher.add(provenance(0), 'a', (event) => order.push(event))
+    vi.advanceTimersByTime(REMOTE_EVENT_BATCH_FLUSH_INTERVAL_MS)
+    expect(order).toEqual(['a', 'flushed'])
+    // Explicit flushes leave forwarding to the caller.
+    batcher.add(provenance(1), 'b', (event) => order.push(event))
+    batcher.flush()
+    expect(order).toEqual(['a', 'flushed', 'b'])
+    fail = true
+    batcher.add(provenance(2), 'c', (event) => order.push(event))
+    vi.advanceTimersByTime(REMOTE_EVENT_BATCH_FLUSH_INTERVAL_MS)
+    expect(order).toEqual(['a', 'flushed', 'b', 'error'])
+    batcher.dispose()
+  })
+
   it('rethrows a failed commit and stays failed so later checkpoints are never committed', () => {
     vi.useFakeTimers()
     const onError = vi.fn()
@@ -55,7 +98,7 @@ describe('RemoteEventBatcher', () => {
     const onCommitted = vi.fn()
     const batcher = new RemoteEventBatcher<string>({ persist, onError })
     batcher.add(provenance(0), 'a', onCommitted)
-    vi.advanceTimersByTime(50)
+    vi.advanceTimersByTime(REMOTE_EVENT_BATCH_FLUSH_INTERVAL_MS)
     expect(onError).toHaveBeenCalledWith(new Error('disk full'))
     expect(() => batcher.add(provenance(1), 'checkpoint')).toThrow('disk full')
     expect(() => batcher.flush()).toThrow('disk full')