`markdown` was declared only in the `matrix` optional extra, and the
official Docker image installs `--extra all --extra messaging --extra
anthropic --extra bedrock --extra azure-identity --extra hindsight` —
notably NOT `--extra matrix` (the matrix extra is deliberately routed to
lazy-install because `mautrix[encryption]`/`python-olm` can't build on
Windows/macOS — see the 2026-05-12 policy comment in `[all]`).
Result: `markdown` never lands in the image venv, so the Markdown->HTML
conversion on the DEFAULT delivery path silently falls back to plain
text. Cron/agent deliveries render raw `##`/`**`/tables in clients like
Element (no `formatted_body`). The conversion is now used by BOTH
`gateway/platforms/matrix.py` and `tools/send_message_tool.py`, so it is
no longer matrix-specific.
`markdown` is a pure-Python `py3-none-any` wheel (~108KB, no compiled
extensions, no platform constraints), so none of the reasons the matrix
extra was lazy-routed apply to it. Promote it to a core dependency so it
ships in the wheel, the Docker image, and every install; drop the now
redundant copies from the `matrix` extra and the `platform.matrix`
lazy-deps group; refresh the stale "installed with the matrix extra"
docstring.
Verified against a real build: ran the image's exact `uv sync` command
(same extras, no `--extra matrix`) in a clean container off the new
lockfile -> `import markdown` succeeds (3.10.2). On `origin/main` the
same command leaves markdown absent. 223 targeted tests pass
(test_matrix.py + test_lazy_deps.py).
Closes#32486.
b434f8c3e0