Revert: webpack-dev-server 5.2.4 (#33628) — to verify jquery screenshot regression

[aleksei-semikozov]

Diagnostic revert of #33628 (webpack-dev-server 5.2.3 → 5.2.4).

Purpose: confirm that #33628 is the trigger for stable jquery screenshot test regression on 26_1.

Background:

• Visual tests on master 26_1 currently fail stably with 4 jquery screenshot tests: jquery(1/3)-material, jquery(3/3)-material, jquery(1/3)-fluent, jquery(3/3)-fluent
• Plus various flaky failures: angular/vue tests, scheduler, accessibility, etc.
• Bisection shows: last green CI was 3e3aa561 (TreeView TreeView: Item text alignment shifts for nodes with expand/collapse icons when the width is narrow and text overflows (T1329043) #33661). First stable red was d9629585 (chore(deps): update dependency webpack-dev-server to v5.2.4 [security] #33628 webpack-dev-server). Single commit in between.
• Diagnostic PR [test] Empty commit from master to isolate jquery regression #33671 (empty commit from master HEAD with .gitignore touch) reproduced same 4 jquery failures, confirming master regression independent of any contributor changes.

Expected outcome: if jquery tests pass on this revert PR, #33628 is the cause. Then we need to either:

• Keep this revert merged (re-introduces CVE) until visual tests are stabilized
• Or regenerate screenshot baselines for webpack-dev-server 5.2.4 timing
• Or find different fix path

Note: CVE addressed by #33628 will still be covered by pnpm overrides in #33669 if that PR merges separately.

[aleksei-semikozov]

Diagnostic complete. Reverting #33628 does NOT fix jquery screenshot regression — same 4 tests still fail + 2/3-fluent flakes. Root cause is earlier (likely #33618 Grid Demos csp fix on 2026-05-19). Closing without merge to preserve security fix.