Three tool specs (ty, deptry, import_linter) each duplicated ~40 lines of identical backend dispatch logic to construct a local system hook PreCommitConfig. This adds a single classmethod that encapsulates the pattern.

New method

PreCommitConfig.from_system_hook() handles backend dispatch (prefixing uv run --frozen --offline for uv), system language resolution, and LocalRepo construction internally. It takes only two parameters (hook_id and entry) and hardcodes the common defaults (always_run=True, pass_filenames=False, requires_venv=True, inform_how_to_use_on_migrate=False):

# Before: ~40 lines of if/elif/else per tool
backend = get_backend()
if backend is BackendEnum.uv:
    return PreCommitConfig.from_single_repo(
        pre_commit_schema.LocalRepo(repo="local", hooks=[
            pre_commit_schema.HookDefinition(
                id="ty", name="ty",
                entry="uv run --frozen --offline ty check",
                language=get_system_language(), ...
            )
        ]),
        requires_venv=True, inform_how_to_use_on_migrate=False,
    )
elif backend is BackendEnum.none:
    # Same thing without the uv prefix...
else:
    assert_never(backend)

# After
return PreCommitConfig.from_system_hook(
    hook_id="ty",
    entry="ty check",
)

Changes

• src/usethis/_tool/pre_commit.py — Added from_system_hook() classmethod with 2 params (hook_id, entry), hardcoding always_run=True, pass_filenames=False
• src/usethis/_tool/impl/spec/{ty,deptry,import_linter}.py — Replaced backend dispatch blocks with single from_system_hook() calls; removed now-unused imports (get_backend, assert_never, BackendEnum, pre_commit_schema, get_system_language)
• tests/usethis/_tool/test_pre_commit.py — 10 tests covering both backends, all hook fields, and hardcoded defaults

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