chore: release v0.4.1

[hunterdsp]

Patch release, docs only — cut so the corrected README reaches PyPI, which
re-renders the long description on publish and nowhere else.

Contents

• make-run documented at last: a page under Libraries covering all five
  functions, the undefined-is-not-empty rule, and why the queries use a
  sentinel makefile rather than --eval.
• Every documented source path fixed. They said src/; scripts have lived in
  src/just_bashit/ since 0.2.0, so every copied . just-bashit/src/… line
  failed — including out of an unpacked release tarball.
• README gained install, the jb / jbx / jb-inspect entry points, and a
  make-run section; its layout diagram matched nothing on disk.
• make docs-coverage gate: a shipped script with no page, or a page missing
  from nav, now fails inside make lint.
• docs/release.md step 4 notes that two of its checkboxes are now enforced.

No behaviour changes — every src/just_bashit/ diff in this PR is the version
header bump.

Verification

• make version-check — pyproject.toml, jb.toml, just-runit, and all src/
  headers agree at 0.4.1.
• make lint clean, make docs-check clean.
• 0.4.0's docs are already live; this release is what carries them to PyPI.

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