fix(leader): derive hookline for DWG leaders; size it from the dim style

DWG stores no "hookline exists" flag (only the direction bit), so every
DWG-loaded leader kept hookline_enabled=false and drew no hook. Derive
it: a text-annotated leader hooks when its final segment leaves the
horizontal by more than 15°, shared by the render and snap/grip paths.

Hook length comes from the dim style like the arrowhead (DIMASZ ×
DIMSCALE), and with DIMTAD "text above" it extends under the annotation
to the far edge of the MTEXT's laid-out extents — newly exposed by
acadrust (lock bumped); the old text-height heuristic stays as the
no-style fallback.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Cargo.lock

@@ -74,7 +74,7 @@ checksum = "366ffbaa4442f4684d91e2cd7c5ea7c4ed8add41959a31447066e279e432b618"
 [[package]]
 name = "acadrust"
 version = "0.4.0"
-source = "git+https://github.com/OpenAEC-Foundation/acadifc?branch=main#a87435fc9eb8e47788176eab444a49a64876ca91"
+source = "git+https://github.com/OpenAEC-Foundation/acadifc?branch=main#3832a9b6f598405f057e6e4e6d49db65f4d68834"
 dependencies = [
  "ahash 0.8.12",
  "anyhow",
@@ -3180,7 +3180,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b577e2d69827c4740cba2b52efaad1c4cc7c73042860b199710b3575c68438d"
 dependencies = [
  "bytecount",
- "memchr 1.0.2",
+ "memchr 2.8.3",
  "nom 8.0.0",
 ]