Unify terminal display-width helpers

key_help, selector and control each carried their own East Asian width
and truncation logic with slightly different rules, and cli clipped tmux
labels by code point, so a CJK display name ran twice as wide as an
ASCII one before its ellipsis appeared.

Move the cell-width helpers into herdr_hub.text, make truncate_label
cell-aware, and sanitise control characters before curses draws a row
so an escape sequence in a remote error cannot be rendered as ^[ and
misalign the list.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

herdr_hub/text.py

@@ -0,0 +1,104 @@
+"""Terminal cell-width helpers shared by the popups and tmux labels.
+
+curses and tmux lay text out in cells: East Asian wide characters take two,
+combining marks and zero-width format characters none. Each popup used to
+carry its own copy of this logic with slightly different rules, and tmux
+labels were clipped by code point, so CJK names truncated inconsistently.
+"""
+from __future__ import annotations
+
+import unicodedata
+
+
+ZERO_WIDTH_CATEGORIES = frozenset({"Mn", "Me", "Cf", "Cc"})
+
+
+def char_width(character: str) -> int:
+    if (
+        unicodedata.combining(character)
+        or unicodedata.category(character) in ZERO_WIDTH_CATEGORIES
+    ):
+        return 0
+    return 2 if unicodedata.east_asian_width(character) in {"W", "F"} else 1
+
+
+def display_width(text: str) -> int:
+    """Number of terminal cells ``text`` occupies."""
+    return sum(char_width(character) for character in text)
+
+
+def truncate_display(text: str, width: int) -> str:
+    """Longest prefix of ``text`` that fits in ``width`` cells."""
+    if width <= 0:
+        return ""
+    used = 0
+    for index, character in enumerate(text):
+        size = char_width(character)
+        if used + size > width:
+            return text[:index]
+        used += size
+    return text
+
+
+def display_tail(text: str, width: int) -> str:
+    """Longest suffix of ``text`` that fits in ``width`` cells."""
+    if width <= 0:
+        return ""
+    used = 0
+    for index in range(len(text) - 1, -1, -1):
+        size = char_width(text[index])
+        if used + size > width:
+            return text[index + 1 :]
+        used += size
+    return text
+
+
+def pad_display(text: str, width: int) -> str:
+    """Clip or space-pad ``text`` to exactly ``width`` cells."""
+    clipped = truncate_display(text, width)
+    return clipped + " " * max(0, width - display_width(clipped))
+
+
+def sanitize_display(text: str) -> str:
+    """Replace control characters, which curses would render as ``^X``."""
+    return "".join(
+        " " if unicodedata.category(character) == "Cc" else character
+        for character in text
+    )
+
+
+def wrap_display(text: str, width: int) -> list[str]:
+    """Hard-wrap at cell boundaries; newlines break, control characters blank."""
+    lines: list[str] = []
+    line = ""
+    cells = 0
+    for character in text:
+        if character == "\n":
+            lines.append(line)
+            line, cells = "", 0
+            continue
+        if unicodedata.category(character) == "Cc":
+            character = " "
+        size = char_width(character)
+        if cells + size > width and line:
+            lines.append(line)
+            line, cells = "", 0
+        line += character
+        cells += size
+    lines.append(line)
+    return lines
+
+
+def input_display_line(prompt: str, value: str, width: int) -> str:
+    """``prompt: value`` clipped to ``width`` cells, keeping the end of the value."""
+    prefix = f"{prompt}: "
+    if display_width(prefix) >= width:
+        return truncate_display(prefix, width)
+    value_width = width - display_width(prefix)
+    if display_width(value) <= value_width:
+        visible_value = value
+    elif value_width <= 1:
+        visible_value = "…"[:value_width]
+    else:
+        visible_value = "…" + display_tail(value, value_width - 1)
+    return prefix + visible_value