TUI: Zeichen am rechten Rand bei schmalen Terminals nicht mehr abgeschnitten

ContinuousBookViews vertikale Scrollbar reserviert 2 Spalten, die vorher
nicht aus der Wrap-Breite herausgerechnet wurden — der Text wurde also
2 Zeichen breiter gewrappt, als tatsächlich sichtbar war, wodurch die
Scrollbar die letzten 1-2 Buchstaben jeder Zeile überdeckt hat. Bei
schmalen Terminals (großer Font, wenig Spalten) war das besonders
auffällig, betraf strukturell aber jede Breite.

Fix: overflow-x: hidden (eine ungewollte horizontale Scrollbar hat
zusätzlich eine Zeile unten geklaut) + overflow-y: scroll (hält die
Scrollbar-Breite von Anfang an konstant, kein Rätselraten je nach
Inhaltsgröße) in book_view.py. reader_screen.py misst die Wrap-Breite
jetzt am Container statt an book_view selbst (vermeidet einen
Miss-nach-Einschränken-Zirkelbezug bei wiederholten Resizes) und rechnet
die feste Scrollbar-Breite (SCROLLBAR_GUTTER=2) heraus; beim Anwenden
des Layouts wird sie wieder daraufgerechnet, damit book_view.styles.width
weiterhin fürs Zentrieren passt.

Getestet: content_region-Breite stimmt jetzt exakt mit der Wrap-Breite
über sechs verschiedene Terminalbreiten (60-200 Spalten, inkl. des
120-Zeichen-Cap-Bereichs) überein — vorher lag sie durchgehend 2 Spalten
darunter. Voller Regressionstest (Scroll, Fußnote, Resize) läuft weiter
fehlerfrei.

tui/diora_tui/book_view.py

@@ -15,6 +15,18 @@ from .layout import BookLayout
 
 
 class ContinuousBookView(ScrollView):
+    # We always wrap text to fit exactly, so a horizontal scrollbar should
+    # never be needed — and "scroll" (not "auto") for the vertical one keeps
+    # its gutter reserved from the very first (still-empty) layout pass, so
+    # the width we wrap text at later never has to guess whether a scrollbar
+    # will appear and steal columns out from under already-wrapped lines.
+    DEFAULT_CSS = """
+    ContinuousBookView {
+        overflow-x: hidden;
+        overflow-y: scroll;
+    }
+    """
+
     def __init__(self, book_layout: BookLayout) -> None:
         super().__init__()
         self.book_layout = book_layout
@@ -24,6 +36,7 @@ class ContinuousBookView(ScrollView):
         _scroll_x, scroll_y = self.scroll_offset
         row = scroll_y + y
         strips = self.book_layout.row_strips
+        width = self.scrollable_content_region.width
         if row < 0 or row >= len(strips):
-            return Strip.blank(self.size.width, self.rich_style)
+            return Strip.blank(width, self.rich_style)
-        return strips[row].crop_extend(0, self.size.width, self.rich_style)
+        return strips[row].crop_extend(0, width, self.rich_style)

tui/diora_tui/reader_screen.py

@@ -29,6 +29,11 @@ from .statusbar import StatusBar
 
 MAX_LINE_WIDTH = 120
 AUTOSAVE_INTERVAL = 5.0
+# ContinuousBookView forces its vertical scrollbar always-on (see book_view.py)
+# so this stays constant — measuring the container's width and subtracting
+# this fixed amount avoids a measure-after-constrain race against book_view's
+# own (possibly already-constrained-from-a-previous-layout) width.
+SCROLLBAR_GUTTER = 2
 
 _EMPTY_LAYOUT = layout.BookLayout(starts=[], heights=[], row_strips=[], total_rows=0, width=1)
 
@@ -81,7 +86,8 @@ class ReaderScreen(Screen):
     def compose(self):
         yield Header()
         yield LoadingIndicator(id="reader-loading")
-        with Container(id="reader-scroll"):
+        with Container(id="reader-scroll") as scroll_container:
+            self._scroll_container = scroll_container
             # Stays visible (empty) from the start rather than toggling display
             # on once loaded — a widget that's just been switched from hidden
             # to visible hasn't been through a layout pass yet, so its `.size`
@@ -93,6 +99,17 @@ class ReaderScreen(Screen):
         yield Footer()
 
     def on_mount(self) -> None:
+        # Deferred rather than read synchronously here: right after mount the
+        # container hasn't been through a layout pass yet, so its size isn't
+        # reliable — same lesson as the scroll-restore race below.
+        self.call_after_refresh(self._start_loading)
+
+    def _start_loading(self) -> None:
+        if self._scroll_container.size.width == 0:
+            # Not sized yet after all — keep deferring instead of guessing a
+            # fixed number of refresh cycles (mirrors _restore_position below).
+            self.call_after_refresh(self._start_loading)
+            return
         self._load_book(self._content_width())
 
     @work(thread=True)
@@ -116,11 +133,21 @@ class ReaderScreen(Screen):
         self.set_interval(AUTOSAVE_INTERVAL, self._autosave)
 
     def _content_width(self) -> int:
-        return max(20, min(MAX_LINE_WIDTH, self.size.width - 4))
+        # Measuring the *container* rather than book_view's own size avoids a
+        # measure-after-constrain race: once a layout has been applied,
+        # book_view's width is pinned to a previous value via styles.width
+        # (below), so re-measuring book_view itself on a later resize would
+        # just read that stale pinned width back instead of the new
+        # available space. The container's width is unaffected by that.
+        available = self._scroll_container.size.width - SCROLLBAR_GUTTER
+        return max(20, min(MAX_LINE_WIDTH, available))
 
     def _apply_layout(self, book_layout: layout.BookLayout, width: int) -> None:
         self.book_layout = book_layout
-        self._book_view.styles.width = width
+        # Pin book_view's outer width to content-width-plus-scrollbar so its
+        # *inner* content region (what render_line actually draws into) ends
+        # up exactly `width` — matching what block texts were wrapped at.
+        self._book_view.styles.width = width + SCROLLBAR_GUTTER
         self._book_view.book_layout = book_layout
         self._book_view.virtual_size = Size(width, book_layout.total_rows)
         self._book_view.refresh()