Matrix outbound markdown was hitting the shared `resolveMarkdownTableMode`
"code" fallback for every send because the Matrix channel plugin never
declared `defaultMarkdownTableMode` in its `messaging` block at
`extensions/matrix/src/channel.ts:452`. Tables were emitted as
`<pre><code>` fenced blocks across every Matrix client.
This change declares `defaultMarkdownTableMode: "bullets"`, matching the
Signal and WhatsApp precedent at `extensions/signal/src/shared.ts:111`
and `extensions/whatsapp/src/shared.ts:261`. The choice matches the
cross-client compatibility profile the issue filer surveyed:
Element X iOS squashes HTML `<table>` and Element X Android drops cell
text entirely (element-hq/element-x-android#1551), while bullet lists
render cleanly across every Matrix client. Operators wanting the
previous fenced-code rendering can set `channels.matrix.markdown.tables:
"code"` explicitly; clients that do render real tables can opt in with
`channels.matrix.markdown.tables: "off"` (markdown-it's `table` rule is
already enabled by default through the markdown-it default preset, so
raw markdown tables flow through to native HTML tables on that path).
Docs and the changelog entry list Matrix alongside Signal and WhatsApp
as a bullet-default channel.
Fixes#78990.
09a2d6e571