fix(fs): remove temp dirs on `dispose`

chore: remove unused @std/fs

feat: `cmd.mock` stubs any command by default

feat: `mock` no longer returns a disposable

This enables you to write `beforeEach(() => mock())`

perf(fs): optimize routine to get spies

docs: bump jsr:@chiezo/bddoc to 0.0.4

chore: exclude `.github/` from publish

fix(fs): mock async ops with `use` correctly

chore: initial alpha version (#1)