docs: document the packaging bump tool

AGENTS.md

@@ -60,5 +60,9 @@ repo-wide reformat as a side effect of an unrelated change.
 
 `.forgejo/workflows/release.yml` fires on a `v*` tag: it asserts that the tag,
 the `pyproject.toml` version and `beefy_player.__version__` all agree, then
-publishes release notes. It does **not** touch packaging, so bump
-`contrib/aur/PKGBUILD` (and its `.SRCINFO`) and the tap's formula by hand.
+publishes release notes. It does **not** touch packaging, so run
+`tools/bump_packaging.py <version>` after publishing: it rewrites
+`contrib/aur/PKGBUILD` and regenerates its `.SRCINFO` from it, rewrites the tap
+formula in `contrib/homebrew`, and with `--commit` commits the tap first and
+then this repository. Both channels build the sdist attached to the release,
+so they hash the same asset.

README.md

@@ -338,6 +338,11 @@ repaint it with the gradient.
 `uvx ruff check .` is the enforced lint. The tree is not `ruff format`-clean (54
 files would change), so do not reformat it wholesale.
 
+`tools/bump_packaging.py <version>` keeps the AUR package and the Homebrew tap
+formula in step with a release — it rewrites `PKGBUILD`, regenerates
+`.SRCINFO` from it (no makepkg needed), rewrites the formula, and `--commit`s
+both. `--check` reports drift without writing.
+
 Pushes run the test suite (`.forgejo/workflows/tests.yml`); a `v*` tag runs
 `release.yml`, which checks that the tag, `pyproject.toml` and
 `beefy_player.__version__` agree and then publishes the release notes. It does