fix: restore JumpStyle seek slider and fix fractional truncation bug

- Add JumpStyle(QProxyStyle) to player_header.py so clicking the seek
  bar jumps to the clicked position (lost during player_header extraction)
- Fix _on_slider_user_action: int(frac) always truncated to 0
  (e.g. 500/1000=0.5 → int(0.5)=0), now emits raw value 0-1000
- Fix _on_user_seek_frac: properly converts slider value (0-1000) to
  playback position with bounds clamping

src/app.py

@@ -379,8 +379,13 @@ class MainWindow(QMainWindow):
         if self.audio_output:
             self.audio_output.setVolume(value / 100.0)
 
-    def _on_user_seek_frac(self, frac: int):
+    def _on_user_seek_frac(self, value: int):
-        self.player.setPosition(int(frac * self.player.duration()))
+        duration = self.player.duration()
+        if duration <= 0:
+            return
+        new_pos = int(value / 1000.0 * duration)
+        new_pos = max(0, min(duration - 1, new_pos))
+        self.player.setPosition(new_pos)
 
     def _on_player_position(self, position: int):
         duration = self.player.duration()

src/ui/player_header.py

@@ -1,5 +1,5 @@
 from PyQt6.QtWidgets import (
-    QWidget, QHBoxLayout, QVBoxLayout, QPushButton, QLabel, QSlider, QGroupBox, QStyle,
+    QWidget, QHBoxLayout, QVBoxLayout, QPushButton, QLabel, QSlider, QGroupBox, QStyle, QProxyStyle,
 )
 from PyQt6.QtCore import Qt, pyqtSignal
 from PyQt6.QtGui import QPixmap, QColor
@@ -11,6 +11,13 @@ def _fmt_time(ms: int) -> str:
     return f"{m}:{s:02d}"
 
 
+class JumpStyle(QProxyStyle):
+    def styleHint(self, hint, opt=None, widget=None, returnData=None):
+        if hint == QStyle.StyleHint.SH_Slider_AbsoluteSetButtons:
+            return Qt.MouseButton.LeftButton.value
+        return super().styleHint(hint, opt, widget, returnData)
+
+
 class PlayerHeader(QGroupBox):
     prev_requested = pyqtSignal()
     play_pause_requested = pyqtSignal()
@@ -54,6 +61,7 @@ class PlayerHeader(QGroupBox):
         self.time_label_start.setAlignment(Qt.AlignmentFlag.AlignRight | Qt.AlignmentFlag.AlignVCenter)
 
         self.position_slider = QSlider(Qt.Orientation.Horizontal)
+        self.position_slider.setStyle(JumpStyle(self.position_slider.style()))
         self.position_slider.setMinimum(0)
         self.position_slider.setMaximum(1000)
         self.position_slider.setValue(0)
@@ -95,8 +103,7 @@ class PlayerHeader(QGroupBox):
         layout.addLayout(now_playing_layout)
 
     def _on_slider_user_action(self):
-        frac = self.position_slider.value() / 1000.0
+        self.position_changed_by_user.emit(self.position_slider.value())
-        self.position_changed_by_user.emit(int(frac))
 
     def set_cover(self, pixmap: QPixmap = None, tooltip: str = ""):
         if pixmap: