refactor(text): SDF for all text kinds; remove the legacy stroke text path

SDF is the only text renderer now — the stroke path and its LOD ladder are
gone, and the remaining text kinds render as SDF glyph quads too.

- ATTDEF / ATTRIB: carry a GlyphRun so single-line attribute text renders as
  SDF (multi-line already did via layout_mtext). Tolerance / complex-linetype
  text already SDF.
- Remove `sdf_text_enabled()` (the OCS_TEXT_SDF flag / kill switch) and take
  the SDF path unconditionally everywhere: tessellate Text arm (per-group by
  GlyphRun presence), hit_test fallbacks, render gather, complex_lt, table,
  mleader.
- Delete the text LOD ladder: tess.rs baseline/greek block and the
  block_cache greek/baseline path (emit_greeked_text / emit_text_baseline),
  plus the now-dead helpers text_baseline_points / text_greek_obb_tris /
  text_obb_corners_native / mtext_line_count and the LocalWire
  text_height_local / text_obb_local fields. All text is crisp at every zoom;
  text entities are exempt from the sub-pixel stub cull.
- Fix a latent bug: block-internal SDF text was culled because its LocalWire
  aabb_local was [0,0,0,0] (no points) — fold the glyph-quad extent into
  aabb_local and exempt text_verts-carrying wires from the sub-pixel cull.
- Clear the pre-existing dead-code warnings (TextPlacement.elevation, TabKind,
  MTextRunKind::Tab).

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

src/entities/text.rs

@@ -53,8 +53,6 @@ pub(crate) fn sync_text_alignment_point(t: &mut Text) {
 pub struct TextPlacement {
     /// Run-local origin (glyph space `[0,0]` maps here), WCS xy, kept f64.
     pub origin: [f64; 2],
-    /// Entity elevation (WCS z).
-    pub elevation: f64,
     pub height: f32,
     pub rotation: f32,
     pub width_factor: f32,
@@ -232,7 +230,6 @@ pub fn text_run_placement(t: &Text, document: &acadrust::CadDocument) -> TextPla
     ];
     TextPlacement {
         origin,
-        elevation: wsz,
         height: t.height as f32,
         rotation,
         width_factor,