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/commands.rs

@@ -2788,6 +2788,39 @@ impl H7CAD {
             "PRINT"|"PLOT"|"EXPORT" => {
                 return Task::done(Message::PlotExport);
             }
+            // PLOTSTYLE — load or clear CTB/STB plot style table
+            cmd if cmd == "PLOTSTYLE" || cmd.starts_with("PLOTSTYLE ") => {
+                let sub = cmd.split_once(' ')
+                    .map(|(_, r)| r.trim().to_uppercase())
+                    .unwrap_or_default();
+                match sub.as_str() {
+                    "CLEAR" | "NONE" => {
+                        return Task::done(Message::PlotStyleClear);
+                    }
+                    "" | "LOAD" => {
+                        let active = self.active_plot_style.as_ref()
+                            .map(|t| format!("Active: {}", t.name))
+                            .unwrap_or_else(|| "No plot style loaded.".into());
+                        self.command_line.push_info(&active);
+                        return Task::done(Message::PlotStyleLoad);
+                    }
+                    "?" | "STATUS" => {
+                        let msg = self.active_plot_style.as_ref()
+                            .map(|t| format!(
+                                "Plot style: {}  ({} color overrides)",
+                                t.name,
+                                t.aci_entries.iter().filter(|e| e.color.is_some()).count()
+                            ))
+                            .unwrap_or_else(|| "No plot style table loaded.".into());
+                        self.command_line.push_output(&msg);
+                    }
+                    _ => {
+                        self.command_line.push_error(
+                            "Usage: PLOTSTYLE [LOAD | CLEAR | STATUS]"
+                        );
+                    }
+                }
+            }
             "PAGESETUP" => {
                 if self.tabs[i].scene.current_layout == "Model" {
                     self.command_line.push_error("PAGESETUP: switch to a paper space layout first.");

src/app/mod.rs

@@ -86,6 +86,10 @@ pub(super) struct H7CAD {
     /// Plot scale: "Fit" | "1:1" | "1:2" | "1:4" | "1:5" | "1:10" | "1:20" | "1:50" | "1:100" | "2:1".
     page_setup_scale: String,
 
+    // ── Plot Style Table ──────────────────────────────────────────────────
+    /// Currently loaded CTB/STB table (None = no override).
+    active_plot_style: Option<crate::io::plot_style::PlotStyleTable>,
+
     // ── DimStyle Dialog ───────────────────────────────────────────────────
     dimstyle_open: bool,
     /// Name of the style currently shown in the dialog.
@@ -324,6 +328,13 @@ pub enum Message {
     PlotExport,
     /// Callback after the user picks (or cancels) the export path.
     PlotExportPath(Option<std::path::PathBuf>),
+    // ── Plot Style Table ─────────────────────────────────────────────────
+    /// Open file dialog to load a CTB/STB plot style table.
+    PlotStyleLoad,
+    /// Callback when the user picks (or cancels) a CTB/STB file.
+    PlotStyleLoaded(Option<crate::io::plot_style::PlotStyleTable>),
+    /// Clear the active plot style table.
+    PlotStyleClear,
     // ── DimStyle Dialog ───────────────────────────────────────────────────
     DimStyleDialogOpen,
     DimStyleDialogClose,
@@ -383,6 +394,8 @@ impl H7CAD {
             page_setup_offset_y: "0.0".to_string(),
             page_setup_rotation: "0".to_string(),
             page_setup_scale: "Fit".to_string(),
+            // Plot style
+            active_plot_style: None,
             // DimStyle dialog
             dimstyle_open: false,
             dimstyle_selected: "Standard".to_string(),

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;