feat(app): add fixed Start tab with welcome page and recent documents

A pinned "Start" tab now lives at index 0. It cannot be closed, opens
on launch, and replaces the model-space viewport with a welcome page —
similar to Thunderbird's first-run screen.

- Boot opens with only the Start tab; Drawing1 is no longer auto-spawned.
- The Properties left panel becomes a Recent Documents rail on the
  Start tab. Recents persist to disk
  (%APPDATA%/H7CAD/recent.txt on Windows, $XDG_CONFIG_HOME/H7CAD/recent.txt
  on Linux, ~/Library/Application Support/H7CAD/recent.txt on macOS), up
  to 20 entries, saved on every open and rehydrated at boot.
  Each row opens or removes the file in place.
- The Support ribbon group (Donate / Report / About / Changelog) is
  retired; the same actions surface on the welcome page instead. The
  Donate button is the primary call-to-action — solid #B03020 brand
  fill with a soft brand-tinted ambient glow halo behind the action row
  (Thunderbird-style coloured glow against the neutral page).
- Drawing-only overlays (mouse-area, viewcube, navbar, dynamic input,
  selection markers) are suppressed on the Start tab so its clicks
  don't trigger CAD commands. OpenFile's "current_is_empty" check
  refuses to replace the Start tab, and TabClose ignores requests on
  it.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

src/modules/home/about.rs

@@ -1,5 +1,6 @@
 use crate::modules::{IconKind, ModuleEvent, ToolDef};
 
+#[allow(dead_code)]
 pub fn tool() -> ToolDef {
     ToolDef {
         id: "ABOUT",

src/modules/home/changelog.rs

@@ -1,5 +1,6 @@
 use crate::modules::{IconKind, ModuleEvent, ToolDef};
 
+#[allow(dead_code)]
 pub fn tool() -> ToolDef {
     ToolDef {
         id: "CHANGELOG",

src/modules/home/donate.rs

@@ -1,5 +1,8 @@
 use crate::modules::{IconKind, ModuleEvent, ToolDef};
 
+// Kept for the command-line route ("DONATE" cmd) and possible future ribbon
+// re-introduction; currently the Start tab invokes the same command directly.
+#[allow(dead_code)]
 pub fn tool() -> ToolDef {
     ToolDef {
         id: "DONATE",

src/modules/home/mod.rs

@@ -31,10 +31,7 @@ impl CadModule for HomeModule {
             angular_dim, leader_cmd, linear_dim, mleader_cmd, mtext, radius_dim, text,
         };
         use crate::modules::insert::{create_block, insert_block};
-        use about;
-        use changelog;
         use clipboard::{copy_clip, cut, paste};
-        use donate;
         use draw::{arc, circle, ellipse, hatch, line, polyline, shapes};
         use groups::{group, ungroup};
         use layers::{
@@ -45,7 +42,6 @@ impl CadModule for HomeModule {
             translate, trim,
         };
         use properties::match_prop;
-        use report;
 
         vec![
             RibbonGroup {
@@ -223,15 +219,8 @@ impl CadModule for HomeModule {
                     cut::tool().into(),
                 ],
             },
-            RibbonGroup {
-                title: "Support",
-                tools: vec![
-                    RibbonItem::LargeTool(donate::tool()),
-                    report::tool().into(),
-                    about::tool().into(),
-                    changelog::tool().into(),
-                ],
-            },
+            // Support group lives on the Start tab now (see view.rs:
+            // start_page_view). Removed from the Home ribbon to declutter.
         ]
     }
 }

src/modules/home/report.rs

@@ -1,5 +1,6 @@
 use crate::modules::{IconKind, ModuleEvent, ToolDef};
 
+#[allow(dead_code)]
 pub fn tool() -> ToolDef {
     ToolDef {
         id: "REPORT",