perf: reuse buffers across files
html::Formatter keeps the bump arena, the doc arena's vectors, and the tree's vectors from one file to the next, moving them between lifetimes by collecting empty vectors in place. The CLI keeps one per worker. Pages on one thread: 59 to 56 ms, vue: 26 to 22 ms.
Parent9886cb8
3 files changed+123-50
StackedSplit