refactor(agent-launch): launching into a paired-server workspace stops closing local agent tabs (#29015)

* refactor(agent-launch): a paired-workspace launch stops closing local agent tabs

The prune existed because a local tab in a paired workspace once could not be closed (its close went
only to the host). Today a local id closes locally and the host close no-ops, and every present-day
launch into a paired workspace creates its tab through the host, under a host-surface id.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* test(agent-launch): say how a local tab in a paired workspace closes

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

src/renderer/src/lib/launch-agent-in-new-tab-web-runtime.test.ts

@@ -82,7 +82,7 @@ describe('launchAgentInNewTab paired web runtime', () => {
   })
 
   it('delegates agent quick launch to the host runtime', async () => {
-    store.tabsByWorktree['wt-1'].push({ id: 'stale-agent-tab', launchAgent: 'claude' })
+    store.tabsByWorktree['wt-1'].push({ id: 'local-agent-tab', launchAgent: 'claude' })
     const { launchAgentInNewTab } = await import('./launch-agent-in-new-tab')
 
     const result = launchAgentInNewTab({
@@ -111,7 +111,8 @@ describe('launchAgentInNewTab paired web runtime', () => {
     await Promise.resolve()
     // Why: host creation is async, so the user may be viewing another worktree by the time it lands.
     expect(mocks.setActiveTabType).toHaveBeenCalledExactlyOnceWith('terminal', 'wt-1')
-    expect(mocks.closeTab).toHaveBeenCalledWith('stale-agent-tab', { reason: 'cleanup' })
+    // A local tab closes locally (the host close no-ops), so a launch leaves it alone.
+    expect(mocks.closeTab).not.toHaveBeenCalled()
   })
 
   it('forwards prompt launch env and captured config to the host runtime', async () => {

src/renderer/src/lib/launch-agent-web-host-tab.ts

@@ -5,7 +5,6 @@ import {
   createWebRuntimeAgentSessionTerminalWithLaunchDraft,
   createWebRuntimeSessionTerminal
 } from '@/runtime/web-runtime-terminal-creation'
-import { isWebTerminalSurfaceTabId } from '../../../shared/terminal-surface-id'
 import type { AgentStartupPlan } from '@/lib/tui-agent-startup'
 import type { Tab } from '../../../shared/tab-types'
 import type { TuiAgent } from '../../../shared/tui-agent'
@@ -13,24 +12,11 @@ import type { AgentPromptDelivery } from '../../../shared/agent-session-host-aut
 import { translate } from '@/i18n/i18n'
 import { toAgentLaunchPreferences } from '../../../shared/agent-launch-preferences'
 
-function removeStaleLocalAgentTabsForWebHostLaunch(worktreeId: string): void {
-  const state = useAppStore.getState()
-  for (const tab of state.tabsByWorktree[worktreeId] ?? []) {
-    if (tab.launchAgent && !isWebTerminalSurfaceTabId(tab.id)) {
-      // Why: pruning a stale local agent tab is a system close — keep it out of
-      // the Cmd+Shift+T reopen stack.
-      state.closeTab(tab.id, { reason: 'cleanup' })
-    }
-  }
-}
-
 /**
  * Launch an agent terminal on the web runtime host instead of a local tab.
  *
  * Why: paired web tabs are host-owned, so this path never creates a local tab
- * (callers return tabId: null). Local-only agent tabs cannot be closed because
- * close routes through session.tabs.close on the host, so prune them before
- * the host snapshot.
+ * (callers return tabId: null).
  */
 export function launchAgentInWebHostTab(args: {
   agent: TuiAgent
@@ -66,7 +52,6 @@ export function launchAgentInWebHostTab(args: {
   const launchPreferences = toAgentLaunchPreferences(startupPlan.sessionOptions)
   const structuredPromptDelivery: AgentPromptDelivery =
     promptDelivery === 'draft' ? 'draft' : 'auto-submit'
-  removeStaleLocalAgentTabsForWebHostLaunch(worktreeId)
   const launch = {
     worktreeId,
     environmentId,
@@ -101,9 +86,6 @@ export function launchAgentInWebHostTab(args: {
     outcome: Awaited<ReturnType<typeof createWebRuntimeSessionTerminal>>
     promptDelivered: boolean
   }): { delivered: boolean; failureNotified: boolean } => {
-    // Why: created means the host accepted the launch, not that a local tab
-    // exists; keep pruning stale local rows until the snapshot mirrors.
-    removeStaleLocalAgentTabsForWebHostLaunch(worktreeId)
     if (outcome.status === 'failed') {
       toast.error(
         outcome.message ||