refactor(text): per-entity SDF text — all text kinds, selection/hover highlight

Rearchitect SDF text from a document-wide collector to per-entity
production during tessellation, so each entity owns its glyph quads and
composite/nested text is covered for free (no re-explosion, no per-frame
document walk).

- WireModel gains `text_verts`: glyph quads ride on the wire, so they are
  cached by the tess memo, cloned on hit, and transformed by the block
  expand loop exactly like `points`.
- Text arm (tessellate.rs) builds the quads when SDF is on and suppresses
  the strokes; render gathers text_verts from the viewport wire set
  (`gather_text_verts`, cached on wire content id) — the old collector is
  removed. Covers model, dimension, table, block-internal and paper-sheet
  text uniformly.
- MLEADER text (lays out via layout_mtext, not the Text arm) gets its own
  SDF branch driven by the per-run GlyphRun.
- Pick box comes from the rendered glyph quads (true text extent), not
  entity_aabb which mis-places the box for MTEXT; composite paths no longer
  clobber the empty text wire's tight AABB (dim pick box hugs the text).
- Selection / hover highlight via a text-highlight overlay (upload_text_
  highlight, keyed on selection_generation) mirroring the selected-wire
  xray overlay; base glyphs stay neutral so a deselect leaves no stale tint.
- Debug: env OCS_TEXT_BOX draws each run's glyph-bounds rectangle.

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

src/scene/model/wire_model.rs

@@ -82,6 +82,13 @@ pub struct WireModel {
     /// Low residual paired with [`fill_tris`] (double-single). Empty = all-zero;
     /// tessellation from CAD f64 fills it so fills stay precise at UTM scale.
     pub fill_tris_low: Vec<[f32; 3]>,
+    /// SDF glyph quads for this entity's text (TEXT / MTEXT / dimension text /
+    /// block-internal text). Non-empty only when SDF text is enabled and this
+    /// wire carries a text run. Rides with the wire so it is cached by the
+    /// tess memo, cloned on hit, and transformed by the block-expand loop
+    /// exactly like `points` — no separate collector pass. The renderer
+    /// gathers these across all wires into the text vertex buffer.
+    pub text_verts: Vec<crate::scene::pipeline::text_gpu::TextVertex>,
 }
 
 impl WireModel {
@@ -129,6 +136,7 @@ impl WireModel {
     /// Create a solid wire (no dash pattern, 1px weight).
     pub fn solid(name: String, points: Vec<[f32; 3]>, color: [f32; 4], selected: bool) -> Self {
         Self {
+            text_verts: Vec::new(),
             name,
             points,
             points_low: Vec::new(),
@@ -261,6 +269,7 @@ impl WireModel {
 impl Default for WireModel {
     fn default() -> Self {
         Self {
+            text_verts: Vec::new(),
             name: String::new(),
             points: Vec::new(),
             points_low: Vec::new(),