[johnhldiver-beep]

Fixes #277.

DOMTokenList.toggle(token, force) treated an explicitly-passed undefined second argument as false instead of as an omitted argument (Web IDL optional-boolean semantics). Repro on base: with the token absent, toggle('test', undefined) returned false and failed to add; with the token present it already removed and returned false.

Fix (1 line, in both esm/dom/token-list.js and the committed mirror cjs/dom/token-list.js): else if (force || arguments.length === 1) → else if (force || force === undefined). One-arg calls behave identically (force is undefined then too); explicit true/false force behaviour is unchanged.

Tests: 4 regression assertions in test/html/element.js beside the existing toggle tests (present+undefined removes and returns false; absent+undefined adds and returns true). New tests failed before the fix (absent case: expected true, got false); node test/html/element.js and the full node test/index.js suite both exit 0 with no failures after the fix. Honest limits: this suite prints no numeric assertion totals, so counts are reported as exit codes + failure-grep counts; eslint/tsc and the full npm test (eslint + benchmark + c8) were not run (only runtime deps installed).

Note: prior PR #334 covered the same concern but was closed unmerged because its author voluntarily withdrew it to clean a backlog — not a maintainer rejection. Adjacent open PR #336 (class-attribute parse perf) does not touch toggle.