A pin on the title bar, and no more notch

Pointing at a tile's top edge already brings its bar back, which left the
notch doing half a job: it could still hide a bar, but hiding one tile at a
time stopped being the interesting question once the whole dashboard could
fold its bars at once. It is gone.

In its place, a pin beside each tile's label. Pinned, that tile keeps its
bar while auto-hide is on — for the one or two tiles whose controls are
wanted at a glance. It sits next to the label rather than out with the gear
and ✕ because it is about the bar, not about the tile's contents, and it
stays faint until the tile is pointed at or the pin is on, so a wall of
unpinned tiles is not a wall of pins.

Fullscreen keeps its own rule: every bar folds, pinned or not, because that
is a mode for watching. What it loses with the notch it gets back better —
the same hover at a tile's top edge peeks a bar there too, and now as an
overlay, so peeking no longer pushes the tile's content down and disturbs
the auto-fit. The peek timer the notch needed goes with it.

Per-tile `headHidden` gives way to `headPinned` in the layout, on disk and
on the server.

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

README.md

@@ -209,18 +209,21 @@ below. Nothing is installed without someone clicking.
   gap; alone in its columns it stays as it is. Nothing is saved — the layout
   reverts when you leave fullscreen. A layout deeper than the screen keeps
   its normal row height and scrolls.
-- A tile's actions (menus, text size, clear…) live in its **title bar**;
-  the small **notch** on the bar's bottom edge hides/shows the whole bar
-  for a clean wall-display look. A hidden bar is not gone: point at the
-  tile's top edge and it slides back in over the content, where its buttons
-  click and its width drags the tile exactly as before — so a dashboard can
-  be arranged with every bar out of the way.
-- **Auto-hide bars** (the button left of ⛶) folds every title bar away at
-  once, for a windowed screen that should read like a wall display. It is
-  off on a fresh dashboard and saves with the layout — including a named
-  layout on the server, so a booth loads its screen with the bars already
-  tucked away. Fullscreen folds the bars away regardless; this is the
-  windowed equivalent, asked for by hand. The menu bar's handle is the **ProdDash
+- A tile's actions (menus, text size, clear…) live in its **title bar**.
+- **Auto-hide bars** (the button left of ⛶) folds every title bar away, for
+  a windowed screen that should read like a wall display. A folded bar is
+  not a gone bar: point at the tile's top edge and it slides back in over
+  the content, where its buttons click and its width drags the tile exactly
+  as before — so a dashboard can be arranged with every bar out of the way.
+  The switch is off on a fresh dashboard and saves with the layout —
+  including a named layout on the server, so a booth loads its screen with
+  the bars already tucked away. Fullscreen folds every bar regardless, and
+  the same hover brings one back there too.
+- The **pin** beside a tile's title keeps *that* tile's bar showing while
+  auto-hide is on — for the one or two tiles whose controls are wanted at
+  a glance. It turns the accent colour when it is on and saves with the
+  layout. Fullscreen still folds a pinned bar with the rest.
+- The menu bar's own handle is the **ProdDash
   name itself**, wrapped in a translucent green pill at the left — click it
   to hide the bar; the slim green lip it leaves at the top-left edge brings
   the bar back. It stays at the left so it never sits on top of a tile's