Unverified breakpoints after 2.12.1 release

Type: Bug

launch.json configuration:

```
{
"log": {
"fileLevel": {
"default": "Debug"
},
"fileName": "${workspaceFolder}/logs/ffdebug.log"
},
"name": "FFdebug",
"pathMappings": [
{
"path": "${workspaceFolder}/app/",
"url": "http://127.0.0.1:5500"
},
{
"path": "${workspaceFolder}/app/",
"url": "https://proto.example.com/"
},
{
"path": "${workspaceFolder}/app/",
"url": "https://stage.example.com/"
}
],
"preLaunchTask": "Firefox debugger",
"request": "attach",
"skipFiles": [
"**/js.stripe.com/**/*",
"**/static.sumsub.com/**/*",
"**/node_modules/**/*",
"**/*.min.js",
"${workspaceFolder}/app/lib/tools.js"
],
"host": "127.0.0.1",
"type": "firefox"
}
```

After upgrading to 2.12.1 release and restarting the debugger, I'm unable to verify any of the breakpoints. I have tried to restart both the IDE and the browser to get it to work, but then it would catch a breakpoint in the newly opened tab and don't show it in the IDE.
I have to close all tabs in the browser but one and restart the debugger to connect it again.

Extension version: 2.12.1
VS Code version: Code 1.96.2 (fabdb6a30b49f79a7aba0f2ad9df9b399473380f, 2024-12-19T10:22:47.216Z)
OS version: Windows_NT x64 10.0.19045
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|Intel(R) Core(TM) i3-8145U CPU @ 2.10GHz (4 x 2304)|
|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
vulkan: disabled_off
webgl: enabled
webgl2: enabled
webgpu: enabled
webnn: disabled_off|
|Load (avg)|undefined|
|Memory (System)|7.86GB (0.24GB free)|
|Process Argv|--folder-uri file:///d%3A/Profiles/anrdaemon/Documents/hk/invapi-php|
|Screen Reader|no|
|VM|0%|

The report only identifies launch.json and the Firefox debugger configuration; no source file, test, or entry point is named. First reproduce the unverified-breakpoint behavior with the supplied multi-tab and pathMappings setup in VS Code 1.96.2 and extension 2.12.1, then investigate debugger attachment and breakpoint verification; done means breakpoints remain verified and appear in the IDE across the reported tab setup.

Written by the indexing model from the issue text.