feat(standards): ISO-25 and ANSI dimension, text and leader style presets as pinned data

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

engineering/standards/mleaderstyles.py

@@ -0,0 +1,66 @@
+"""Multileader style presets: arrow, landing gap, text style and height.
+
+Sized to match the dimension presets they sit beside (ISO-25: 2.5 mm arrows
+and lettering; ANSI: 3 mm), so a leader note and a dimension on the same
+sheet read at one size. Only ezdxf can author an MLEADERSTYLE object;
+ActiveX exposes no collection for it (see ``backends/contracts/styles.py``).
+"""
+
+from __future__ import annotations
+
+import math
+from typing import Any
+
+__all__ = ["MLEADER_KEYS", "MLEADER_PRESETS", "resolve_mleaderstyle"]
+
+MLEADER_PRESETS: dict[str, dict[str, Any]] = {
+    "iso": {"arrow_size": 2.5, "landing_gap": 1.0, "text_style": "ISOCP", "text_height": 2.5},
+    "ansi": {"arrow_size": 3.0, "landing_gap": 1.5, "text_style": "ROMANS", "text_height": 3.0},
+}
+
+MLEADER_KEYS: tuple[str, ...] = ("arrow_size", "landing_gap", "text_style", "text_height")
+
+_ILLEGAL_NAME_CHARS = frozenset('<>/\\":;?*|,=`')
+
+
+def _positive(key: str, value: Any, *, allow_zero: bool = False) -> float:
+    if isinstance(value, bool) or not isinstance(value, (int, float)):
+        raise TypeError(f"{key}: expected a number, got {type(value).__name__}")
+    number = float(value)
+    if not math.isfinite(number):
+        raise ValueError(f"{key}: {value!r} is not a finite number")
+    if number < 0.0 or (number == 0.0 and not allow_zero):
+        raise ValueError(f"{key}: {value!r} must be greater than 0")
+    return number
+
+
+def resolve_mleaderstyle(preset: str, overrides: dict | None = None) -> dict[str, Any]:
+    """The preset's four values with ``overrides`` applied; refusals name the key."""
+    key = str(preset).strip().lower() if preset is not None else ""
+    if key not in MLEADER_PRESETS:
+        raise ValueError(f"preset: unknown value {preset!r}; use one of {sorted(MLEADER_PRESETS)}")
+    values = dict(MLEADER_PRESETS[key])
+    if overrides is None:
+        return values
+    if not isinstance(overrides, dict):
+        raise TypeError(f"overrides: expected a mapping, got {type(overrides).__name__}")
+    for raw_key, value in overrides.items():
+        name = str(raw_key).strip().lower()
+        if name not in MLEADER_KEYS:
+            raise ValueError(
+                f"overrides: {raw_key!r} is not a leader style key; allowed: {list(MLEADER_KEYS)}"
+            )
+        if name == "text_style":
+            if not isinstance(value, str) or not value.strip():
+                raise ValueError("text_style: a text style name cannot be empty")
+            bad = sorted(set(value.strip()) & _ILLEGAL_NAME_CHARS)
+            if bad:
+                raise ValueError(
+                    f"text_style: {value!r} contains characters DXF forbids in a name: {bad}"
+                )
+            values[name] = value.strip()
+        elif name == "landing_gap":
+            values[name] = _positive(name, value, allow_zero=True)
+        else:
+            values[name] = _positive(name, value)
+    return values