Setting `canSelectMany` to `true` of `window.createQuickPick` will cause a UI issue

[Alive-Fish]

Type: Bug

1. Download the extension sample https://github.com/microsoft/vscode-extension-samples/tree/main/quickinput-sample.
2. Add one line input.canSelectMany = true in Line 248 under quickinput-sample\src\multiStepInput.ts.
3. F5 to start this extention.
4. Ctrl+Shift+P -> Quick input samples -> multiStepInput
5. Move the mouse over the selectAll button and it is hard to click.

As I saw in Developer Tool, it seems a style class named quick-input-visible-count has wrong value. The screenshot is as below.

This is a simple reproduced step of this issue. Our product has used it and has been reported from customers. Our original usage is https://github.com/OfficeDev/microsoft-365-agents-toolkit/blob/a5e68adb92533eb4b90696c3f59c5a77b6ba6fd7/packages/vscode-extension/src/qm/vsc_ui.ts

VS Code version: Code - Insiders 1.107.0-insider (13086c7, 2025-12-03T18:18:58.648Z)
OS version: Windows_NT x64 10.0.26200
Modes:

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-9700K CPU @ 3.60GHz (8 x 3600)
GPU Status	2d_canvas: enabled direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off trees_in_viz: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	63.84GB (37.62GB free)
Process Argv	--crash-reporter-id bc217dae-ffe3-417e-b3e2-981779672f28
Screen Reader	no
VM	0%

Extensions (19)

Extension	Author (truncated)	Version
azurite	Azu	3.35.0
esbuild-problem-matchers	con	0.0.3
vscode-eslint	dba	3.0.21
gitlens	eam	2025.12.304
prettier-vscode	esb	11.0.2
copilot-chat	Git	0.34.2025120102
vscode-azureresourcegroups	ms-	0.11.7
vscode-dotnet-runtime	ms-	2.4.1
black-formatter	ms-	2025.2.0
debugpy	ms-	2025.16.0
flake8	ms-	2025.2.0
isort	ms-	2025.1.13251007
python	ms-	2025.18.0
vscode-pylance	ms-	2025.10.3
vscode-python-envs	ms-	1.13.13371705
windows-ai-studio	ms-	0.26.3
vscode-yaml	red	1.20.2025120208
vscode-adaptive-cards	Tea	0.1.3
vscode-ai-foundry	Tea	0.12.4

A/B Experiments

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dwcopilot:31158714
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copilot_t_ci:31333650
g012b348:31231168
pythonrdcb7:31268811
pythonpcpt1cf:31399617
6518g693:31302842
6abeh943:31336334
envsactivate1:31349248
editstats-enabled:31346256
cloudbuttont:31366566
aihoversummaries_t:31413033
qwen_all_req:31396049
3efgi100_wstrepl:31403338
trigger-command-fix:31379601
auto_model_enabled:31396818
use-responses-api:31390341
je187915:31401257
afag3459:31419922
agentic_ask_h7d75428:31406124
copilot-nes-oct-t:31418112
metis_rerank_treatment1:31411021
terminalsuggestenabled:31421703
none:31426257
cp_cls_c_966_ss:31426491
chatvisible:31417128
expandedtokens:31418009
inlinechat_v2_hd992725:31426642
c0683394:31426860
decaj161:31422462
find_all_ref_in_bg_f:31420846
9cj19850:31423615
478ah919:31426749
ge8j1254_inline_auto_hint_haiku:31426887
no_diagnostics:31426891
b53de340:31426751
a5gib710:31426879
5j92g670_sonnet:31426790
request_with_suggest:31426864
rename_enabled:31426869
nes-joint-1:31426897
7a04d226_do_not_restore_last_panel_session:31427629
anthropic_thinking_t:31427198

[jrieken]

Still seeing this with insiders 1eea41f3b8dcd80f2f2b49e1a8e3cd859872c8f5

The check-all btn is there and can be clicked but it seems to select the OK button instead of selecting all items