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/scene/view/render.rs

@@ -798,9 +798,6 @@ impl Scene {
         wire_content_id: u64,
     ) -> std::sync::Arc<Vec<crate::scene::pipeline::text_gpu::TextVertex>> {
         use std::sync::Arc;
-        if !crate::scene::text::sdf_atlas::sdf_text_enabled() {
-            return Arc::new(Vec::new());
-        }
         {
             let cache = self.sdf_text_cache.borrow();
             if let Some((id, verts)) = cache.as_ref() {