TS Perf degradation since last version upgrade

Type: Bug

Working on TS files, performace has degraded drastically since the last version upgrade (I have auto update on).
Intellisense is stuck, saving takes more than 30s (format on save is on), seems to be stuck on "Organize imports".

VS Code version: Code 1.98.0 (Universal) (6609ac3d66f4eade5cf376d1cb76f13985724bcb, 2025-03-04T21:06:18.612Z)
OS version: Darwin arm64 24.3.0
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|Apple M2 Max (12 x 2400)|
|GPU Status|2d_canvas: enabled
canvas_oop_rasterization: enabled_on
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
video_decode: enabled
video_encode: enabled
webgl: enabled
webgl2: enabled
webgpu: enabled
webnn: disabled_off|
|Load (avg)|10, 15, 8|
|Memory (System)|32.00GB (14.16GB free)|
|Process Argv|--crash-reporter-id 0b94ffbf-7f47-46d4-ba50-f0cce0fcd724|
|Screen Reader|no|
|VM|0%|
Extensions (20)

Extension|Author (truncated)|Version
---|---|---
gitlens|eam|16.3.2
EditorConfig|Edi|0.17.1
prettier-vscode|esb|11.0.0
codespaces|Git|1.17.3
copilot|Git|1.277.0
copilot-chat|Git|0.25.0
vscode-github-actions|git|0.27.1
vscode-pull-request-github|Git|0.106.0
vscode-docker|ms-|1.29.4
playwright|ms-|1.1.13
debugpy|ms-|2025.4.0
python|ms-|2025.2.0
vscode-pylance|ms-|2025.3.1
remote-containers|ms-|0.401.0
cmake-tools|ms-|1.20.53
cpptools|ms-|1.24.2
cpptools-extension-pack|ms-|1.3.1
svg-preview|Sim|2.8.3
code-spell-checker|str|4.0.40
cmake|twx|0.0.17

(1 theme extensions excluded)

A/B Experiments

```
vsliv368cf:30146710
vspor879:30202332
vspor708:30202333
vspor363:30204092
pythonvspyt551cf:31249601
vscod805cf:30301675
binariesv615:30325510
py29gd2263:31024239
c4g48928:30535728
azure-dev_surveyone:30548225
962ge761:30959799
2e7ec940:31000449
pythontbext0:30879054
cppperfnew:31000557
dwnewjupyter:31046869
nativerepl2:31139839
pythonrstrctxt:31112756
nativeloc1:31192215
iacca1:31171482
5fd0e150:31155592
dwcopilot:31170013
6074i472:31201624
dwoutputs:31242946
customenabled:31248079
9064b325:31222308
copilot_t_ci:31222730
f5992895:31254866
jda6j935:31233686

```

Start by reproducing the slowdown in VS Code 1.98.0 on Darwin arm64 with TypeScript files, focusing on Intellisense, format on save, and Organize imports. Compare behavior with the previous version and isolate the regression; done means saving and language features return to normal performance.

Written by the indexing model from the issue text.