feat: command history navigation with up/down arrow keys

CommandLine now records every submitted command in a recall list (up to
50 entries).  Pressing ↑ in the command input walks back through the
list, ↓ moves forward, and returning to the newest position restores
the draft text the user had typed before navigating.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

src/app/mod.rs

@@ -176,6 +176,10 @@ pub enum Message {
     CommandInput(String),
     CommandSubmit,
     Command(String),
+    /// Recall previous command in history (↑ arrow key).
+    CommandHistoryPrev,
+    /// Recall next command in history (↓ arrow key).
+    CommandHistoryNext,
     ToggleLayers,
     LayerToggleVisible(usize),
     LayerToggleLock(usize),

src/app/update.rs

@@ -248,7 +248,21 @@ impl H7CAD {
                 Task::none()
             }
 
-            Message::CommandInput(s) => { self.command_line.input = s; Task::none() }
+            Message::CommandInput(s) => {
+                // Any manual typing resets the history recall cursor.
+                self.command_line.input = s;
+                Task::none()
+            }
+
+            Message::CommandHistoryPrev => {
+                self.command_line.history_prev();
+                Task::none()
+            }
+
+            Message::CommandHistoryNext => {
+                self.command_line.history_next();
+                Task::none()
+            }
 
             Message::CommandSubmit => {
                 let i = self.active_tab;

src/app/view.rs

@@ -320,6 +320,12 @@ impl H7CAD {
                             {
                                 Some(Message::DeleteSelected)
                             }
+                            keyboard::Key::Named(keyboard::key::Named::ArrowUp) => {
+                                Some(Message::CommandHistoryPrev)
+                            }
+                            keyboard::Key::Named(keyboard::key::Named::ArrowDown) => {
+                                Some(Message::CommandHistoryNext)
+                            }
                             keyboard::Key::Named(keyboard::key::Named::F3) => {
                                 Some(Message::ToggleSnapEnabled)
                             }