Welcome tab icon overlaps with default icon when using VS Code Modern Icons

Type: Bug

### Description
When activating the icon theme, the Welcome tab icon is overlapping/rendering directly on top of the default VS Code tab icon instead of replacing it properly or rendering cleanly.

### Steps to Reproduce
1. Install and activate the Icon Theme.
2. Open the **Welcome** page (`Cmd + Shift + P` -> `Help: Welcome`).
3. Observe the icon rendered on the `Welcome` tab.

### Expected Behavior
The extension icon should cleanly display on the Welcome tab without overlapping or glitching over the default tab icon.

### Actual Behavior
The custom icon and the default tab icon overlap on top of each other.

### Screenshots

VS Code version: Code 1.136.1 (a44adf7f53e00964ab890f9f8758a334f1fc15bc, 2026-09-03T05:06:41Z)
OS version: Darwin arm64 25.6.0
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|Apple M3 Pro (11 x 2400)|
|GPU Status|2d_canvas: enabled
GPU0: VENDOR= 0x106b [Google Inc. (Apple)], DEVICE=0x0000 [ANGLE (Apple, ANGLE Metal Renderer: Apple M3 Pro, Version 26.6.2 (Build 25G83))], DRIVER_VENDOR=Apple, DRIVER_VERSION=26.6.2 *ACTIVE*
Machine model name: Mac
Machine model version: 15.6
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: enabled_on
trees_in_viz: disabled_off
video_decode: enabled
video_encode: enabled
webgl: enabled
webgpu: enabled
webnn: disabled_off|
|Load (avg)|3, 3, 3|
|Memory (System)|18.00GB (0.30GB free)|
|Process Argv|--crash-reporter-id 4c513d50-95a6-453f-88ae-4f5d81395e8c|
|Screen Reader|no|
|VM|0%|
Extensions (3)

Name|Identifier|Author|Version
---|---|---|---
Claude Code for VS Code|anthropic.claude-code|Anthropic|2.1.261
Dart|dart-code.dart-code|Dart-Code|3.142.0
Flutter|dart-code.flutter|Dart-Code|3.142.0

A/B Experiments

```
vsliv368:30146709
vswsl492:30256859
binariesv615:30325510
nativeloc1:31344060
dwcopilot:31170013
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythonrdcb7:31342333
6518g693:31463988
aj953862:31281341
4f60g487:31327383
envsactivate1:31551504
cloudbuttont:31379625
3efgi100_wstrepl:31403338
56b7f661:31457055
ddidt:31399633
ec5jj548:31422691
cp_cls_t_966_ss:31526232
4je02754:31572277
c3h7c220:31478652
cp_cls_t_1081:31454832
conptydll_true:31498968
e9c30283:31461165
46204921:31447328
control_6dc23131:31576178
ei9d7968:31496641
chat:31457767
8hig5102:31480529
89g7j272:31518289
i2gc6536:31499202
52612955:31516516
githubstableflight:31469463
h08i8180_copy:31475368
ddid_t:31478206
hmra_i5g22:31518061
7df3h592:31512476
cp_cls_t_1082:31535311
logging_enabled_new:31498466
db5d2638:31499441
jb_cp_cls_t_632:31543129
56dj4588:31512888
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ha629193:31508444
jh5f2457_c:31540921
jbcp_cls_pctr_t:31531130
cp_intellij_t_nes:31548657
gf14b233:31526830
ahp-both-windows:31556933
ihg5j128:31534457
9gg7f176:31542112
sandbox-ui-on-2:31543161
nes-ex-cf-euporie-03:31542868
enable_editor_pane_layout:31569726
allow-none:31555437
36h42362:31564511
c7c27ce7:31554789
1h923230:31564177
0dg73464:31554319
treatment-23-1:31555779
unuse_dynamic_mcp:31555281
0d8dfbc3:31570291
nemo-v2:31565334
0c1h4866:31566224
session-archive:31558132
5b8j3302:31564601
mangle-name-control:31572633
allow-signed-out:31574473
multiv2:31574985
2bfb8b39:31576696
permission_prompt_control:1332567
ccr_pr_nudge_adoption:1319471
vsc_wsm_t:1340632
jidc7660:1370295
auto_mode_control:1367906
1g5a5742:1379227

```