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 <[email protected]>

src/scene/text/lff.rs

@@ -193,7 +193,7 @@ pub fn get_font(name: &str) -> &'static Font {
 
 /// Decoration line a token toggles.
 #[derive(Clone, Copy)]
-enum Deco {
+pub(crate) enum Deco {
     Under,
     Over,
     Strike,
@@ -202,7 +202,7 @@ enum Deco {
 /// How a decoration token changes state. `\L`/`\O`/`\K` turn on (idempotent),
 /// `\l`/`\o`/`\k` turn off; `%%u`/`%%o` flip.
 #[derive(Clone, Copy)]
-enum Op {
+pub(crate) enum Op {
     On,
     Off,
     Toggle,
@@ -211,7 +211,7 @@ enum Op {
 /// One unit of a text run after inline-code resolution. Shared by the stroke
 /// (LFF) and shaped (TTF) renderers so both interpret the DXF inline grammar
 /// — `\L…\l` decorations and `%%` specials — identically.
-enum Tok {
+pub(crate) enum Tok {
     /// A renderable character (DXF `%%d`/`%%p`/`%%c`/`%%nnn` already resolved).
     Glyph(char),
     /// A literal space.
@@ -225,7 +225,7 @@ enum Tok {
 
 /// Resolve a run's inline codes into a flat token stream. Mirrors the original
 /// inline parser in `tessellate_text_run` exactly (verified by the golden test).
-fn tokenize_run(text: &str) -> Vec<Tok> {
+pub(crate) fn tokenize_run(text: &str) -> Vec<Tok> {
     let mut toks = Vec::new();
     let mut chars = text.chars().peekable();
     while let Some(ch) = chars.next() {