fix(live): give the timing tower the fold back

The tyre deg panel expanded by default during races and rendered a
placeholder row per driver until enough clean laps existed to fit a
degradation model. For the first third of a race that was ~525px of
'warming up' rows above the Timing Tower, pushing the tower — the thing
the page exists for — off the fold entirely.

The panel now opens when it has something to say rather than because the
session is a race, and says 'collecting clean laps' while it waits. A
reader who toggles it keeps their choice.

Also:
- Hoist degradationModel into a memo shared by the readiness check and the
  rows. It is O(laps) per driver and previously re-ran on every render at
  feed rate.
- Order the side rail most-synthesized to most-raw, so a reader arriving
  mid-session gets 'what just happened' before the regulatory log.
- Fade the trailing edge of the nav below 560px. It scrolls with a hidden
  scrollbar, so the cut-off item read as a clipping bug rather than as
  scrollable.

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

frontend/src/pages/LiveTimingPage.tsx

@@ -289,14 +289,16 @@ export function LiveTimingPage() {
                 session={snapshot.Session}
               />
             </div>
+            {/* Rail runs most-synthesized to most-raw: a reader arriving
+                mid-session wants "what did I miss" before the regulatory log. */}
             <div className="live-rc-col">
+              <EventRail events={events} driverInfo={snapshot.DriverInfo} />
               <TeamRadioTicker
                 captures={snapshot.TeamRadio ?? []}
                 driverInfo={snapshot.DriverInfo}
                 session={snapshot.Session}
               />
               <RaceControlFeed messages={snapshot.RCMessages ?? []} driverInfo={snapshot.DriverInfo} />
-              <EventRail events={events} driverInfo={snapshot.DriverInfo} />
             </div>
           </div>
         </>