feat(text): parse TEXT via acadrust + extend SDF text to MTEXT

Two related steps for the text pipeline:

- TEXT parsing now goes through acadrust's parse_plain_text (like MTEXT
  uses parse_mtext). text::acad_text_encode parses the value's %% codes —
  including %%u/%%o underline/overline and %%nnn — and re-encodes to the
  stroke tessellator's \L/\O + resolved-Unicode grammar, so OCS no longer
  tokenizes TEXT %% codes itself. (ATTRIB/TOLERANCE/DIMENSION still use the
  local tokenizer for now.) Bumps the acadrust pin to the commit that
  completes the TEXT/MTEXT control-code set.

- SDF text (OCS_TEXT_SDF) now covers MTEXT and every text-producing
  entity, not just top-level TEXT. TextStroke carries a GlyphRun (layout
  params); the collector walks convert()'s TruckObject::Text runs and
  applies annotation scale exactly as tessellate does for strokes.
  layout_glyph_quads shares lff::tokenize_run so %% specials resolve and
  \L/\O decorations are skipped (decoration LINES in SDF are still TODO).

Verified: stroke rendering unchanged with the flag off; SDF glyphs render
correctly for TEXT and MTEXT with OCS_TEXT_SDF=1. 154 lib tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/entities/attribute.rs

@@ -292,6 +292,7 @@ fn build_attr_truck(input: AttrTextInputs<'_>, document: &acadrust::CadDocument)
             origin,
             color: None,
             fill_tris,
+            run: None,
         });
     }
     let _ = input.line_count; // round-trip only — recomputed above