Reconnect to remembered hardware instead of pairing every launch

`remembered` was a HashSet inside DeviceRegistry, so it lasted exactly as
long as the process. Every launch started from nothing: find the trainer,
press Connect, find the strap, press Connect, and only then ride. FR-1.5
has been a Should since the beginning and was never actually true.

It is a file now — devices.json in the app data directory, written when a
link actually comes up rather than when Connect is pressed. A Connect the
hardware then refuses is not a pairing, and writing one down would mean a
trainer the rider gave up on getting chased on every launch afterwards.
Forgetting is recorded too, in its own list: absent means never seen,
forgotten means the rider looked at this device and said no, and
auto-connect has to keep honouring that on the next launch as well. The
file is advisory — a corrupt one costs auto-connect, never a ride.

Auto-connect is driven by the scan rather than fired once at startup. The
hardware is asleep at startup — a trainer wakes when the cranks turn, a
strap when it is put on (A-4) — so a remembered device is reconnected the
moment it advertises, through the same path the rider's own click takes,
scan suspension included. Bounded by AUTO_ATTEMPTS on an AUTO_RETRY
cooldown and cleared when the link comes up or the rider connects by
hand: an app that never stops trying can never honestly say it has
stopped (FR-1.11). A device disconnected by hand is left alone for the
rest of the session, since a disconnect that undoes itself two ticks
later is not a disconnect.

Pods now prefer the pod we know. Every Click advertises the same name and
the same type byte, so before this a rider whose partner was warming up
in the next room got whichever pod woke first. With nothing of that kind
remembered anything still goes, or there could never be a first pairing.

And the pair is one pod, not two. Confirmed on this hardware 2026-08-21:
pairing the − pod alone delivers all ten buttons, its twin's included —
which §2.3.1 had established for the frames but not for the pairing. So
take_plus_pod holds the + pod back while a known − pod may merely be
asleep, and connect_controller with no pod named means the − pod rather
than both. The wait is bounded by PLUS_GRACE, because a flat − pod should
cost the rider a D-pad and not a controller, and Buttons is untouched: it
is what makes the handover between the two configurations invisible.

Not yet tested against real hardware — nothing was advertising here. The
store, the retry budget and the pod-preference rules have unit tests, and
a seeded devices.json was confirmed to load and seed the − pod at launch,
but the connect path itself waits for a ride.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ui/src/components/ConnectionScreen.svelte

@@ -92,7 +92,17 @@
       {@const bars = rssiBars(device.rssi)}
       <article class="row" class:live={isConnected(device)}>
         <div class="identity">
-          <span class="name">{device.name}</span>
+          <span class="name">
+            {device.name}
+            <!-- FR-1.5. Paired before, so it comes back on its own the next
+                 time it advertises — this launch or any other. Worth a badge:
+                 it is the difference between a device the rider has to fetch
+                 and one that simply turns up, and Forget below is how they
+                 take it back. -->
+            {#if device.remembered}
+              <span class="badge" title="Paired before — reconnects on its own">Remembered</span>
+            {/if}
+          </span>
           <span class="meta">{KIND_LABEL[device.kind]} · {device.address}</span>
           {#if device.error}
             <span class="error">{device.error}</span>
@@ -324,6 +334,10 @@
   }
 
   .name {
+    display: flex;
+    align-items: baseline;
+    gap: 0.45rem;
+    min-width: 0;
     font-size: 1.12rem;
     font-weight: 600;
     letter-spacing: -0.01em;
@@ -332,6 +346,18 @@
     text-overflow: ellipsis;
   }
 
+  .badge {
+    flex: none;
+    padding: 0.1rem 0.4rem;
+    border: 1px solid var(--hairline);
+    border-radius: 0.3rem;
+    color: var(--ink-dim);
+    font-size: 0.68rem;
+    font-weight: 600;
+    letter-spacing: 0.04em;
+    text-transform: uppercase;
+  }
+
   .meta {
     font-size: 0.8rem;
     color: var(--ink-dim);