ProdCom: direction toggle, icon channels button, leaner tile settings

Three changes to the ProdCom tile, all per-tile and persisted with the
layout (version 1.2.0):

- A title-bar button flips the transcript between top-down (newest at the
  bottom, still the default) and bottom-up. It is CSS only — the entries
  container becomes column-reverse, DOM order is untouched — but everything
  that follows "latest" flips with it: auto-follow, jump-to-latest, the
  near-latest scroll test, and the "New messages" pill, which moves to the
  top of the tile and points up.

- The "Channels ▾" text button is now a funnel icon. It keeps what the
  label carried: while any channel is hidden the icon takes the accent
  color and a compact "3/4" count sits beside it, with the full wording in
  the tooltip.

- Tile settings drop the channel-name filter and text size, both of which
  the title bar already handles, and gain "Show channel icons" for the
  per-entry avatars. Removing the channel filter made its code dead, so
  channelFilter(), filteredOut() and the data-channel-name attribute went
  with it — the menubar's hidden-channel set is now the only filter.

Text size keeps working without a schema entry: the A−/A+ buttons persist
it through saveInstanceSettings, the shell's settings popover only writes
schema keys so it survives an Apply, and the client falls back to 15px when
it is absent. Existing tiles have no saved showAvatars value and the check
is `=== false`, so they keep their icons.

Verified against tools/prodcom-mock.js: both directions render and
auto-follow correctly, the pill appears at the right end and jumps to the
newest entry, the count badge tracks the channel toggles, a tile bumped to
19px kept it across an Apply and a reload, a freshly added tile started at
15px with icons shown, and two tiles held independent state.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -168,8 +168,10 @@ below. Nothing is installed without someone clicking.
 
 - **ProdCom** — live transcript stream with in-place updates of in-progress
   speech, channel colors, per-tile channel visibility toggles and group
-  presets, timestamps, text size and jump-to-latest in the title bar.
+  presets, timestamps, text size, a top-down / bottom-up direction toggle
+  and jump-to-latest in the title bar.
   Admin config: ProdCom server (host : port), API key.
+  Tile settings: channel icons, direction and timestamps.
 - **ProPresenter** — what's live and what's next, with slide progress,
   driven by the shared `propresenter-core` client (ProPresenter 7/20).
   Admin config: ProPresenter endpoint (host : port), password.