v0.123.0

Scaffold teaches a project's own test runner to skip the experiments/ and screenshots/ scratch directories.

Context

Scaffold has created experiments/ and screenshots/ at every project's root
since 0.122.0, and every repository walk rlsbl performs prunes them. That kept
rlsbl's own checks green and said nothing at all to the project's test runner:
a test_*.py left in a scratch directory was still collected by a bare pytest
run, and a .go file there without its own module file was still built by
go test ./... -- so a half-finished probe could break a suite it had nothing to
do with, which is the opposite of what a disposable scratch directory is for.

There is no cross-ecosystem setting for this, so each release target now
declares, as a support axis, the mechanism its own runner honours, from a
closed vocabulary. Python merges both names into pytest's norecursedirs;
because that option replaces pytest's default rather than adding to it, the
default patterns are written back alongside them. Go gets a go.mod in each
scratch directory -- the go command never descends into a directory that
declares its own module -- and the directory's ignore file un-ignores that one
filename, so the marker reaches a fresh clone where a dropped probe would
otherwise break the build. Deno merges both names into deno.json's exclude
array. npm is left out on purpose and says so: its test script names whichever
runner the project chose, and rlsbl writes none of those runners'
configuration files.

pyproject.toml and deno.json belong to the project rather than to scaffold, so
the merges run outside the template pipeline, never enter the managed-files
registry that drives orphan deletion, and preserve everything around the one
setting. Where the setting cannot be placed safely -- a pytest.ini, which
outranks pyproject.toml, or a deno.jsonc, whose comments a rewrite would lose
-- scaffold writes nothing and prints the exact line to add by hand.

Features

• Scratch directories no longer break the suite. rlsbl scaffold now teaches a project's own test runner to skip experiments/ and screenshots/, so a half-finished probe left in one cannot fail a suite it has nothing to do with. Python projects get both names in pytest's norecursedirs (with pytest's own defaults written back beside them), Go projects get a go.mod in each directory so the go command never descends into it, and Deno projects get both names in deno.json's exclude. Your own configuration around the setting is preserved byte for byte, and re-running scaffold changes nothing. npm is left out deliberately: the test script names the runner, whose configuration file rlsbl does not own.