Documentation for the people who can now install it

A documentation release, published the same day as v0.8.0 and for a reason
worth writing down.

The README is also the PyPI description, and every command in it assumed a
cloned repository: make run VIDEO_ID=... DECK=..., make dictionary,
make antonyms, make translate-setup. None of that exists after
pip install tango-anki. The shop window for a package published that
morning was telling its first visitors to run a build tool they did not have.

PyPI freezes a release's description at upload time and will not let it be
edited, so correcting the published page costs a release. That is what this
one is.

What changed

Every command in the README is now a tango subcommand. The Makefile
equivalents are kept, in a collapsed section, for people working in a clone.

The version badge was stuck at v0.5.3, five releases behind, because it
was hardcoded. It now reads live from PyPI and from the GitHub releases API,
next to a new badge for the package. Neither can go stale again.

The roadmap table was wrong about the plan, not just the version. It
still showed the ordering from before 27 August 2026, when packaging sat at
v0.10.0 behind cross-platform support. It now shows the real sequence, where
the project actually is, and the known rough edges.

A .pyc had been committed. .gitignore listed tests/__pycache__ and
src/pipeline/__pycache__ by name, so scripts/__pycache__ was never
covered. Replaced with __pycache__/ and *.py[cod], which catch every
directory including ones that do not exist yet.

.env.example documents the PyPI publishing keys. PYPI_USER must be
the literal string __token__, not an account name. An account name paired
with a pypi- token is rejected with a 403 that does not say why, which is
what tripped this project's first upload.

Upgrading

Nothing to do. No code changed; pip install --upgrade tango-anki only
updates the metadata and the description.

The rung previously numbered v0.8.1, first-run downloads, a Dockerfile and a
real uninstall, is now v0.8.2.

Full detail in CHANGELOG.md.