refactor: standardize timing with monotonic clocks, remove redundant stream parsing

src/pygui/backend/controllers/session_controller.py

@@ -1,6 +1,7 @@
 """QML-facing controller for the live/review wafer dashboard."""
 from __future__ import annotations
 import logging
+import time
 from typing import Any, Optional
 
 from PySide6.QtCore import QObject, Property, QTimer, Qt, Signal, Slot
@@ -325,10 +326,7 @@ class SessionController(QObject):
                     result = -result
                 values.append(result)
             
-            # Create a mock timestamp or use elapsed time since start.
-            # We don't have a time value from the binary stream header right now.
-            t = seq * 0.05  # approx 20Hz if seq increments 1 per frame
-            return Frame(seq=seq, time=t, values=values)
+            return Frame(seq=seq, time=time.monotonic(), values=values)
 
         # Clear out any old data from the prev sessions
         self._model.reset()

src/pygui/serialcomm/stream_reader.py

@@ -32,18 +32,6 @@ class StreamReader:
         self._thread = threading.Thread(target=self._run, daemon = True)
         self._thread.start()
 
-    def _read_exact(self, count: int) -> bytes | None:
-        """Read exactly `count` bytes. Returns None if timed out/stopped."""
-        buf = bytearray()
-        while len(buf) < count and not self._stop.is_set():
-            b = self._transport.read(1)
-            if not b:
-                continue
-            buf.extend(b)
-        if self._stop.is_set():
-            return None
-        return bytes(buf)
-
     def _run(self) -> None:
         try:
             # Check the first few bytes to determine if the wafer is streaming binary, ASCII hex dump, or text lines.
@@ -198,14 +186,12 @@ class StreamReader:
                     values.append(0.0)
             
             try:
-                frame = Frame(seq=seq, time=seq * 0.1, values=values)
+                frame = Frame(seq=seq, time=time.monotonic(), values=values)
                 self._on_frame(frame)
                 seq += 1
             except Exception as exc:
                 log.error("Error emitting ASCII frame: %s", exc)
 
-            time.sleep(0.05)
-
     def _run_text_lines(self, initial_bytes: bytes) -> None:
         log.info("StreamReader: starting line-by-line ASCII text parsing")
         buf = bytearray(initial_bytes)