fix(native-chat): refuse structured chat on every Windows execution path

canUseStructuredNativeChat only refused win32 when a project runtime
resolved, so folder-workspace keys (and other keys with no project
runtime) failed open into structured chat on Windows. Fail closed on
win32 unconditionally after the host check, matching the settings copy:
local macOS/Linux only; Windows/WSL/SSH stay on terminal chat.

src/renderer/src/lib/structured-native-chat-availability.test.ts

@@ -82,4 +82,23 @@ describe('canUseStructuredNativeChat', () => {
       false
     )
   })
+
+  it('refuses a Windows folder workspace even though its key resolves no project runtime', () => {
+    mockGetRendererAppPlatform.mockReturnValue('win32')
+    const state = {
+      ...stateFor({}),
+      activeRepoId: null,
+      activeWorktreeId: null
+    } as unknown as AppState
+    expect(canUseStructuredNativeChat(state, 'folder:folder-1')).toBe(false)
+  })
+
+  it('allows a folder workspace on a non-Windows platform', () => {
+    const state = {
+      ...stateFor({}),
+      activeRepoId: null,
+      activeWorktreeId: null
+    } as unknown as AppState
+    expect(canUseStructuredNativeChat(state, 'folder:folder-1')).toBe(true)
+  })
 })

src/renderer/src/lib/structured-native-chat-availability.ts

@@ -1,5 +1,4 @@
 import type { AppState } from '@/store/types'
-import { getLocalProjectExecutionRuntimeContext } from '@/lib/local-preflight-context'
 import { getExecutionHostIdForWorktree } from '@/lib/worktree-runtime-owner'
 import { getRendererAppPlatform } from '@/lib/renderer-app-platform'
 
@@ -10,13 +9,9 @@ export function canUseStructuredNativeChat(state: AppState, worktreeId: string):
   if (getExecutionHostIdForWorktree(state, worktreeId) !== 'local') {
     return false
   }
-  const projectRuntime = getLocalProjectExecutionRuntimeContext(state, worktreeId)
-  return !(
-    projectRuntime?.status === 'repair-required' ||
-    projectRuntime?.runtime.kind === 'wsl' ||
-    // The shipped Windows process-tree addon may not expose creation time. Until
-    // the host advertises that proof, keep this experimental surface on the
-    // ordinary terminal path instead of letting create fail after the click.
-    (getRendererAppPlatform() === 'win32' && projectRuntime?.runtime.kind === 'windows-host')
-  )
+  // The shipped Windows process-tree addon may not expose creation time. Until
+  // the host advertises that proof, refuse every local Windows execution path —
+  // windows-host, WSL, and keys that resolve no project runtime (folder
+  // workspaces, floating terminal) — so create cannot fail after the click.
+  return getRendererAppPlatform() !== 'win32'
 }