refactor: move resource/IO root modules under io/

Relocate three root-level modules into io/, where they belong by concern:

- update_check.rs -> io/update_check.rs (its own doc-comment notes it
  mirrors how crate::io wraps blocking calls in async).
- patterns.rs, linetypes.rs -> io/ (standard resource catalogs parsed
  from asset files and populated into the document — IO-shaped work).

Fix the moved files' include_str! paths (one level deeper), add the
mod declarations to io/mod.rs, drop them from lib.rs/main.rs, and
re-point all crate:: references to crate::io::. No behavior change.

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

src/app/document.rs

@@ -1,5 +1,5 @@
 use crate::command::CadCommand;
-use crate::linetypes;
+use crate::io::linetypes;
 use crate::modules::draw::modify::refedit::RefEditSession;
 use crate::scene::pick::grip::GripEdit;
 use crate::scene::GripDef;

src/app/layers.rs

@@ -60,7 +60,7 @@ impl OpenCADStudio {
                 } else {
                     lt.name.clone()
                 };
-                let art = crate::linetypes::extract_pattern(&lt.description);
+                let art = crate::io::linetypes::extract_pattern(&lt.description);
                 ui::properties::LinetypeItem { name, art }
             })
             .collect();

src/app/mod.rs

@@ -1476,7 +1476,7 @@ pub enum Message {
     Noop,
     /// GitHub releases API returned a result. `Some(version)` means a
     /// newer release exists; we open the update-notice window.
-    UpdateCheckResult(Option<crate::update_check::UpdateInfo>),
+    UpdateCheckResult(Option<crate::io::update_check::UpdateInfo>),
     /// User dismissed the update-notice window.
     UpdateNoticeClose,
     /// First-launch default-association prompt: user accepted — register this
@@ -2072,7 +2072,7 @@ impl OpenCADStudio {
         s.main_window = Some(id);
         let open_main = open_task.map(|_| Message::Noop);
         let check_update = Task::perform(
-            crate::update_check::check_for_update(),
+            crate::io::update_check::check_for_update(),
             Message::UpdateCheckResult,
         );
         let focus_cmd = s.focus_cmd_input();

src/app/properties.rs

@@ -1,6 +1,6 @@
 use super::helpers::{entity_type_key, entity_type_label, title_case_word};
 use super::{OpenCADStudio, VARIES_LABEL};
-use crate::linetypes;
+use crate::io::linetypes;
 use crate::scene::view::dispatch;
 use crate::ui;
 use acadrust::{EntityType, Handle};

src/app/update/file.rs

@@ -341,7 +341,7 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
                 self.tabs[i].scene.selected = rustc_hash::FxHashSet::default();
                 self.tabs[i].scene.preview_wires = vec![];
                 self.tabs[i].scene.current_layout = "Model".to_string();
-                crate::linetypes::populate_document(&mut self.tabs[i].scene.document);
+                crate::io::linetypes::populate_document(&mut self.tabs[i].scene.document);
                 self.tabs[i].properties = PropertiesPanel::empty();
                 // Seed the current table / multileader style from the file's
                 // header so the ✓ marks the right one (text/dim/mline come from

src/app/update/mod.rs

@@ -537,7 +537,7 @@ impl OpenCADStudio {
                 let i = self.active_tab;
                 self.push_undo_snapshot(i, "CLEAR");
                 self.tabs[i].scene.clear();
-                crate::linetypes::populate_document(&mut self.tabs[i].scene.document);
+                crate::io::linetypes::populate_document(&mut self.tabs[i].scene.document);
                 self.tabs[i].properties = PropertiesPanel::empty();
                 let doc_layers = self.tabs[i].scene.document.layers.clone();
                 let vp_info = self.tabs[i].scene.viewport_list();
@@ -2449,7 +2449,7 @@ impl OpenCADStudio {
                 Task::none()
             }
             Message::UpdateNoticeOpenRelease => {
-                crate::sys::open_url(crate::update_check::RELEASES_PAGE);
+                crate::sys::open_url(crate::io::update_check::RELEASES_PAGE);
                 self.close_active_modal();
                 Task::none()
             }

src/io/linetypes.rs

@@ -69,7 +69,7 @@ pub fn complex_lt(name: &str) -> Option<&'static ComplexLt> {
         .get(&name.to_ascii_uppercase())
 }
 
-const LIN_SOURCE: &str = include_str!("../assets/linetypes/OpenCADStudio.lin");
+const LIN_SOURCE: &str = include_str!("../../assets/linetypes/OpenCADStudio.lin");
 
 // ── Pattern art extraction ────────────────────────────────────────────────
 

src/io/mod.rs

@@ -11,6 +11,9 @@ pub mod print_to_printer;
 pub mod step;
 pub mod stl;
 pub mod xref;
+pub mod linetypes;
+pub mod patterns;
+pub mod update_check;
 
 use crate::scene::DerivedCaches;
 use acadrust::entities::{Dimension, EntityType};
@@ -879,7 +882,7 @@ mod layer_roundtrip_tests {
     // round-trip through `ext`, and return whether every one survived.
     fn roundtrip_layers(ext: &str, count: usize) -> bool {
         let mut doc = CadDocument::new();
-        crate::linetypes::populate_document(&mut doc);
+        crate::io::linetypes::populate_document(&mut doc);
         let names: Vec<String> = (0..count).map(|n| format!("Layer{}", n + 1)).collect();
         for name in &names {
             let mut dl = DocLayer::new(name);

src/io/patterns.rs

@@ -8,7 +8,7 @@
 
 use std::sync::OnceLock;
 
-const PAT_SRC: &str = include_str!("../assets/patterns/OpenCADStudio.pat");
+const PAT_SRC: &str = include_str!("../../assets/patterns/OpenCADStudio.pat");
 
 // ── Public types ──────────────────────────────────────────────────────────
 

src/lib.rs

@@ -6,13 +6,10 @@ pub mod cli;
 pub mod command;
 pub mod entities;
 pub mod io;
-pub mod linetypes;
 pub mod modules;
 pub mod plugin;
-pub mod patterns;
 pub mod scene;
 pub mod snap;
 pub mod ui;
 pub mod par;
 pub mod sys;
-pub mod update_check;

src/main.rs

@@ -10,16 +10,13 @@ mod cli;
 mod command;
 mod entities;
 mod io;
-mod linetypes;
 mod modules;
 mod plugin;
-mod patterns;
 mod scene;
 mod snap;
 mod ui;
 mod par;
 mod sys;
-mod update_check;
 
 fn main() -> iced::Result {
     // Web (wasm) uses the single-window entry; native uses the multi-window

src/scene/model/hatch_patterns.rs

@@ -6,7 +6,7 @@
 
 use std::sync::OnceLock;
 
-use crate::patterns::PatLineDef;
+use crate::io::patterns::PatLineDef;
 use crate::scene::model::hatch_model::{HatchPattern, PatFamily};
 use acadrust::entities::{HatchPattern as DxfPattern, HatchPatternLine};
 use acadrust::types::Vector2;
@@ -65,7 +65,7 @@ fn build_catalog() -> Vec<PatternEntry> {
         pat_lines: vec![],
     }];
 
-    for def in crate::patterns::catalog() {
+    for def in crate::io::patterns::catalog() {
         entries.push(PatternEntry {
             name: def.name.clone(),
             description: def.description.clone(),

src/scene/tess.rs

@@ -665,7 +665,7 @@ pub(crate) fn tessellate_entity(
     // linetype assigned, so we only consult the first wire here — multi-wire
     // returns come exclusively from MTEXT colour splits which can't trigger
     // this path.
-    if let Some(clt) = crate::linetypes::complex_lt(lt_name) {
+    if let Some(clt) = crate::io::linetypes::complex_lt(lt_name) {
         if let Some(base) = bases.first() {
             let mut wires = text::complex_lt::apply_along(
                 &base.name,

src/scene/text/complex_lt.rs

@@ -7,7 +7,7 @@
 //! Shape X → along the linetype direction; Shape Y → perpendicular in XZ.
 
 use crate::entities::text_support::resolve_dxf_special_chars;
-use crate::linetypes::{ComplexLt, LtSegment};
+use crate::io::linetypes::{ComplexLt, LtSegment};
 use crate::scene::text::lff;
 use crate::scene::model::wire_model::WireModel;