feat(viewport): per-tile model render mode, persisted via VPORT entries

Each model-space tile now carries its own visual style instead of one
global mode shared by every pane:

- ModelTile gains a `render_mode`; the active tile renders with the live
  picker mode, inactive tiles keep their stored style, so changing one
  tile no longer changes the others. Split inherits the source style.
- SetRenderMode writes only the active tile; switching the active tile
  mirrors its style back into the tab (picker + live render).
- Persisted through the *Active VPORT entries (acadrust now round-trips
  the render mode via DXF code 281 / DWG RC 281), restored on open for
  both tiled and single-tile model layouts.
- Bump acadrust to pick up the VPORT render-mode field.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

Cargo.lock

@@ -54,7 +54,7 @@ checksum = "366ffbaa4442f4684d91e2cd7c5ea7c4ed8add41959a31447066e279e432b618"
 [[package]]
 name = "acadrust"
 version = "0.3.4"
-source = "git+https://github.com/HakanSeven12/acadrust?branch=main#b6834f22c6761b253f3753b26e2b6aefc23f4ff6"
+source = "git+https://github.com/HakanSeven12/acadrust?branch=main#5b09ccc00d92bb55dcccbef97c0fcecf94417e16"
 dependencies = [
  "ahash",
  "anyhow",
@@ -3176,7 +3176,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b577e2d69827c4740cba2b52efaad1c4cc7c73042860b199710b3575c68438d"
 dependencies = [
  "bytecount",
- "memchr 1.0.2",
+ "memchr 2.8.1",
  "nom 8.0.0",
 ]