sketch: refactor lowlevel server to handler pattern #402

Job	Run time
checks / readme-snippets	11s
checks / pre-commit	34s
checks / test (3.11, lowest-direct, ubuntu-latest)	5m 58s
checks / test (3.10, lowest-direct, ubuntu-latest)	6m 0s
checks / test (3.10, locked, windows-latest)	6m 38s
checks / test (3.11, locked, windows-latest)	6m 19s
checks / test (3.11, locked, ubuntu-latest)	6m 0s
checks / test (3.10, locked, ubuntu-latest)	5m 55s
checks / test (3.11, lowest-direct, windows-latest)	6m 18s
checks / test (3.12, lowest-direct, ubuntu-latest)	6m 4s
checks / test (3.13, locked, windows-latest)	6m 28s
checks / test (3.14, locked, ubuntu-latest)	7m 9s
checks / test (3.12, locked, windows-latest)	6m 41s
checks / test (3.13, lowest-direct, windows-latest)	6m 27s
checks / test (3.12, locked, ubuntu-latest)	5m 59s
checks / test (3.13, lowest-direct, ubuntu-latest)	5m 58s
checks / test (3.14, locked, windows-latest)	7m 17s
checks / test (3.12, lowest-direct, windows-latest)	7m 23s
checks / test (3.14, lowest-direct, windows-latest)	6m 42s
checks / test (3.14, lowest-direct, ubuntu-latest)	6m 8s
checks / test (3.10, lowest-direct, windows-latest)	6m 50s
checks / test (3.13, locked, ubuntu-latest)	5m 53s
all-green	5s
	2h 8m 57s

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