v3 bloats the package size significantly, especially for people not using those features

Nobody has claimed this yet.

### mapbox-gl-js version

3.19.1

### Browser and version

all browsers

### Expected behavior

my bundle sizes shouldn't bloat significantly when upgrading from v2 to v3

### Actual behavior

the version jump from v2 to v3 apparently bloats our vendor bundle by over 700k. So we're rolling back to v2, which raises questions:
1. will v2 remain supported?
2. will there be a way to use v3 without the bloat? Conditional imports? peer packages? Anything?

### Link to the demonstration

_No response_

### Steps to trigger the unexpected behavior

_No response_

### Relevant log output

```shell

```

Start by reproducing the reported 700k vendor-bundle increase between v2 and v3.19.1 across the stated browser targets. Investigate whether conditional imports or peer packages can exclude unused features; done means a measured explanation or a viable way to use v3 without the reported bloat, alongside an answer about v2 support.

Written by the indexing model from the issue text.