Feat: implement CTB/STB plot style table with PDF export integration

- src/io/plot_style.rs: PlotStyleTable and PlotStyleEntry data structures;
  CTB reader (deflate/zlib decompressed text format) with ACI→RGB and
  ACI→lineweight lookup; CTB writer (zlib compressed); LW_TABLE constant
- src/io/pdf_export.rs: accept optional PlotStyleTable; apply ACI color
  and lineweight overrides during PDF rendering
- src/scene/wire_model.rs: add `aci: u8` field to carry ACI index
- src/scene/render.rs: render_style() now returns ACI alongside RGBA
- src/scene/mod.rs + tessellate.rs: propagate aci through wire building
- app: PlotStyleLoad/Loaded/Clear messages and handlers;
  PLOTSTYLE LOAD | CLEAR | STATUS command; active_plot_style state on H7CAD
- flate2 added as dependency

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/update.rs

@@ -2092,6 +2092,7 @@ impl H7CAD {
                     &wires, eff_w, eff_h,
                     draw_ox as f32, draw_oy as f32,
                     rotation_deg, &path,
+                    self.active_plot_style.as_ref(),
                 ) {
                     Ok(()) => self.command_line.push_info(&format!(
                         "Exported: {}",
@@ -2102,6 +2103,29 @@ impl H7CAD {
                 Task::none()
             }
 
+            // ── Plot Style Table ──────────────────────────────────────────────
+            Message::PlotStyleLoad => {
+                Task::perform(
+                    crate::io::pick_plot_style(),
+                    Message::PlotStyleLoaded,
+                )
+            }
+            Message::PlotStyleLoaded(Some(table)) => {
+                self.command_line.push_output(&format!(
+                    "Plot style '{}' loaded ({} color entries).",
+                    table.name,
+                    table.aci_entries.iter().filter(|e| e.color.is_some()).count()
+                ));
+                self.active_plot_style = Some(table);
+                Task::none()
+            }
+            Message::PlotStyleLoaded(None) => Task::none(),
+            Message::PlotStyleClear => {
+                self.active_plot_style = None;
+                self.command_line.push_output("Plot style table cleared.");
+                Task::none()
+            }
+
             // ── DimStyle Dialog ───────────────────────────────────────────────
             Message::DimStyleDialogOpen => {
                 let i = self.active_tab;