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/mod.rs

@@ -710,11 +710,14 @@ pub struct Scene {
     pub(crate) model_tiles: RefCell<Vec<ModelTile>>,
     /// Index of the active model tile (camera input + overlays target it).
     pub(crate) active_model_tile: std::cell::Cell<usize>,
-    /// Cache of the SDF text vertex list, keyed on `(geometry_epoch,
-    /// anno_scale.to_bits())`, so the per-frame collector is not re-laid-out on
-    /// pan / zoom. See [`Scene::sdf_text_vertices`].
+    /// Cache of the gathered SDF text vertex list for one viewport, keyed on
+    /// the wire-buffer content id. The glyph quads ride on each entity's wire
+    /// (built by the tessellator); this caches the per-viewport gather so it is
+    /// not re-walked every frame while the wire set is unchanged. Keyed on the
+    /// wire content id so it re-gathers exactly when the wires (geometry or
+    /// selection) change. See [`Scene::gather_text_verts`].
     sdf_text_cache:
-        RefCell<Option<(u64, u32, std::sync::Arc<Vec<crate::scene::pipeline::text_gpu::TextVertex>>)>>,
+        RefCell<Option<(u64, std::sync::Arc<Vec<crate::scene::pipeline::text_gpu::TextVertex>>)>>,
     /// pane_grid layout tree for the Model tab — the source of truth for the
     /// tile split layout, resize and focus. `model_tiles` (the renderer's
     /// per-pane data: camera / render-mode / grid) is kept in lock-step with