Root cause: jsdom has no layout and CodeMirror measures text ranges in an animation frame, sometimes after a test finished; test files that did not stub Range.getClientRects (e.g. search/codePreview) threw an unhandled TypeError that failed whole CI runs at random (seen on #41).
Fix: stub Range.getClientRects / getBoundingClientRect once in src/test/setup.ts; drop the six per-file copies.
Verified: vitest on editor/lsp, editor/refactor, templates, search (55 files, 458 tests, no unhandled errors).
Claude-Session: https://claude.ai/code/session_01VUYsdXA2nkF5v6zsC93dpn
l0ng-ai