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/__init__.py

@@ -0,0 +1,39 @@
+"""Authored drafting standards data.
+
+Dimension, text and leader style presets live here (track E, group S); the
+system-variable catalogue, paper sizes, plot styles and templates are sibling
+modules added by their own groups and imported by path. Everything in this
+package is data plus validation — no I/O, no ezdxf, no COM — so the backends,
+the tools and the provenance tests read one copy.
+"""
+
+from __future__ import annotations
+
+from engineering.standards.dimstyles import (
+    DIM_VARIABLE_RANGES,
+    DIM_VARIABLE_WHITELIST,
+    PRESET_VARIABLES,
+    PRESETS,
+    check_dim_value,
+    describe_preset,
+    resolve_dimstyle,
+    validate_overrides,
+)
+from engineering.standards.mleaderstyles import MLEADER_PRESETS, resolve_mleaderstyle
+from engineering.standards.textstyles import TEXT_PRESETS, resolve_font, validate_textstyle
+
+__all__ = [
+    "DIM_VARIABLE_RANGES",
+    "DIM_VARIABLE_WHITELIST",
+    "MLEADER_PRESETS",
+    "PRESETS",
+    "PRESET_VARIABLES",
+    "TEXT_PRESETS",
+    "check_dim_value",
+    "describe_preset",
+    "resolve_dimstyle",
+    "resolve_font",
+    "resolve_mleaderstyle",
+    "validate_overrides",
+    "validate_textstyle",
+]