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/scene/convert/acad_to_truck.rs

@@ -19,6 +19,25 @@ pub struct TextStroke {
     pub origin: [f64; 2],
     pub color: Option<[f32; 3]>,
     pub fill_tris: Vec<[f32; 2]>,
+    /// Layout inputs to rebuild this run as per-glyph SDF quads (see
+    /// `scene::text::glyph_quads`). `Some` on runs wired for the SDF text
+    /// renderer; `None` leaves the run to the stroke path only. Heights are
+    /// raw (pre annotation-scale), matching `strokes` — the SDF collector
+    /// applies annotation scale the same way `tessellate` does for strokes.
+    pub run: Option<GlyphRun>,
+}
+
+/// Per-run text-layout inputs needed to reproduce a run as SDF glyph quads.
+#[derive(Clone, Debug)]
+pub struct GlyphRun {
+    pub text: String,
+    pub font: String,
+    /// Raw height in drawing units (annotation scale applied later).
+    pub height: f32,
+    pub rotation: f32,
+    pub width_factor: f32,
+    pub oblique: f32,
+    pub tracking: f32,
 }
 
 #[allow(dead_code)]