Indent-size setting not wired to the editor (CodeMirror indentUnit)

[MrCoder]

Surfaced by the e2e gap suite (SET-4, test.fixme in e2e/tests/settings.spec.js).

Bug: the Settings → indent-size Select renders but settings.indentSize is not connected to the editor. AppRoot.tsx (~1268) threads only theme/fontSize/fontFamily/keymap into <CodeEditor>; nothing sets CM6's indentUnit facet from settings.indentSize. DSL blocks indent a fixed 2 spaces via delimitedIndent (zenumlLanguage.ts) regardless of the setting.

Fix: thread indentSize into the editor and set the indentUnit facet. Then flip SET-4 test.fixme → test.

[MrCoder]

Fixed in PR #828, shipped to prod in release-20260618082047. Indent-size now drives CM6's indentUnit facet (live); SET-4 e2e test flipped from fixme to a real passing test.