fix(hatch): deselect refresh, boundary offset, fill-click

Three hatch fixes:

- Selected hatches are tinted, but the hatch model cache and GPU upload
  were keyed only on geometry_epoch, so Esc cleared the selection set
  without repainting — the hatch stayed blue (#71). Key both on
  selection_generation too.

- add_hatch stored the boundary entity in local render space, so the
  boundary wire re-projected `world_offset` away from the fill on
  offset (large-coordinate) drawings. Build it in WCS.

- Clicking a hatch only selected it on its boundary wire, not its fill.
  Two causes: visible_hatches_for_click used a narrower block-visibility
  test than the render path (fill drawn but not clickable), and
  point_in_polygon closed every NaN sub-path — degrading the explicit
  2-point edge encoding of a boundary into zero-area loops. Mirror the
  render's visibility test and only auto-close sub-paths of >=3 verts.

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

src/scene/pipeline/mod.rs

@@ -119,7 +119,10 @@ pub struct Pipeline {
     /// Last `(geometry_epoch, camera_generation)` value for which GPU buffers
     /// were uploaded. We re-upload when either side changes — pan/zoom bumps
     /// camera_generation, which triggers re-culling and a fresh upload.
-    pub cached_epoch: (u64, u64),
+    /// `(geometry_epoch, camera_generation, selection_generation)` of the
+    /// last static-buffer upload. Selection is tracked so the selected-hatch
+    /// tint refreshes on select / deselect (issue #71).
+    pub cached_epoch: (u64, u64, u64),
     /// Content id of the wire buffer currently resident on the GPU (Phase
     /// 3.2). When the incoming `ViewportData.wire_content_id` matches, the
     /// world-space wire vertices are unchanged (e.g. a pure pan reused the
@@ -899,7 +902,7 @@ impl Pipeline {
             gpu_face3d_fill: None,
             gpu_face3d_edges: vec![],
             viewcube,
-            cached_epoch: (u64::MAX, u64::MAX),
+            cached_epoch: (u64::MAX, u64::MAX, u64::MAX),
             cached_wire_id: u64::MAX,
             cached_selection: (u64::MAX, u64::MAX),
         }