fix: resolve 7 code review issues from v0.4.x

- Fix KSUDP clutch field reading fuel at offset 59 (KSUDP has no clutch input)
- Replace Notify with watch::channel for reliable shutdown (no missed wakeups)
- Deduplicate read_u16 from parser_pcars into shared binary_utils
- Remove dead Display impl for FeedSource
- Remove unused read_i8 helper from binary_utils
- Change Vec<Instant> to [Instant; 50] in FeedState (eliminate heap alloc)
- Cache rarely-changing strings by driver_id in Telemetry Tool parser

src/feed_state.rs

@@ -43,7 +43,7 @@ pub struct FeedState {
     pub last_packet_ago_secs: Option<f64>,
     pub start_time: Option<Instant>,
     pub last_packet_time: Option<Instant>,
-    pub packet_timestamps: Vec<Instant>,
+    pub packet_timestamps: [Instant; RING_CAPACITY],
     pub ring_index: usize,
     pub ring_count: usize,
     pub last_frame: Option<TelemetryFrame>,
@@ -62,7 +62,7 @@ impl FeedState {
             last_packet_ago_secs: None,
             start_time: None,
             last_packet_time: None,
-            packet_timestamps: vec![Instant::now(); RING_CAPACITY],
+            packet_timestamps: [Instant::now(); RING_CAPACITY],
             ring_index: 0,
             ring_count: 0,
             last_frame: None,
@@ -85,9 +85,7 @@ impl FeedState {
         self.last_packet_ago_secs = Some(0.0);
 
         if self.ring_count < RING_CAPACITY {
-            if self.ring_count < self.packet_timestamps.len() {
-                self.packet_timestamps[self.ring_count] = now;
-            }
+            self.packet_timestamps[self.ring_count] = now;
             self.ring_count += 1;
             self.ring_index = self.ring_count % RING_CAPACITY;
         } else {