Files past 2,000 lines stay strictly no-growth (tests included). The message now says how
to offset growth in the same PR: move an existing function into a topical sibling (moved
code keeps its cap) or put new tests in a new test file. Probed on a 2,128-line file: plain
growth blocks; the same growth plus moving a CC-22 function out passes; a new test file
passes; growing the old test file blocks.
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