feat(ui): add press-to-capture shortcut editing to Keyboard Shortcuts dialog

Replace manual key entry with per-row capture cells: clicking + Add
inserts a draft row at the top with its key cell armed, and the next
key combination is recorded and normalized (Ctrl+Shift+S →
CTRL+SHIFT+S). While armed, a dedicated keyboard listener swallows all
input so recorded shortcuts do not execute in the drawing.

Draft rows are transient and confirmed only through an explicit accept
button, so the table never retains empty rows. Duplicate keys and
unrunnable commands are flagged in danger styling with a persistent
warning naming the conflicting command. Added reset-to-defaults with
confirmation, apply-and-exit, a shortcut count, and an unsaved-changes
guard on close.

src/app/mod.rs

@@ -960,6 +960,20 @@ pub(super) struct OpenCADStudio {
     shortcut_bindings: rustc_hash::FxHashMap<String, String>,
     /// Working rows shown by the shortcut editor until Apply is pressed.
     shortcut_editor_rows: Vec<(String, String)>,
+    /// Row whose Key cell is armed for capture: the next key combination
+    /// pressed anywhere fills that row's key. While set, the keyboard
+    /// subscription swallows every key so captured shortcuts do not run in
+    /// the drawing.
+    shortcut_capture_row: Option<usize>,
+    /// True while a freshly added (top) row is an unfinished draft: it exists
+    /// only until its key and command are filled (success) or it is cancelled
+    /// (Esc / ✕ / dialog close), so the list never keeps an empty row.
+    shortcut_pending_add: bool,
+    /// True while the "Reset to default" confirmation is showing.
+    shortcut_reset_confirm: bool,
+    /// True while the "unsaved changes will be discarded" confirmation
+    /// overlays the editor: the user tried to close with un-applied rows.
+    shortcut_close_confirm: bool,
 
     // ── Command Aliases ───────────────────────────────────────────────────
     /// Command-line aliases: uppercase abbreviation → uppercase command
@@ -2552,6 +2566,28 @@ pub enum Message {
     ShortcutEditorAdd,
     ShortcutEditorRemove(usize),
     ShortcutEditorApply,
+    /// Apply the working rows and close the dialog.
+    ShortcutEditorApplyExit,
+    /// The check button on a draft row: finish the addition without applying.
+    ShortcutEditorDraftAccept,
+    /// Show the "Reset to default" confirmation.
+    ShortcutEditorResetAsk,
+    /// Reset bindings and rows to the shipped defaults.
+    ShortcutEditorResetConfirm,
+    /// Hide the reset confirmation without resetting.
+    ShortcutEditorResetDeny,
+    /// Discard un-applied rows and close the editor.
+    ShortcutEditorCloseDiscard,
+    /// Keep editing: hide the discard confirmation.
+    ShortcutEditorCloseKeep,
+    /// The user clicked a row's Key cell: arm capture for that row.
+    ShortcutCaptureStart(usize),
+    /// A key combination was pressed while a row's Key cell was armed.
+    ShortcutCaptureKey(String),
+    /// Disarm capture without filling the row.
+    ShortcutCaptureClear,
+    /// Cancel capture (Esc): also discards an unfinished draft row.
+    ShortcutCaptureCancel,
     /// Canonical key emitted by the global keyboard subscription.
     ShortcutPressed(String),
     // ── Command Alias Editor (ALIASEDIT) ────────────────────────────────
@@ -3414,6 +3450,10 @@ impl OpenCADStudio {
             // Keyboard shortcuts
             shortcut_bindings: rustc_hash::FxHashMap::default(),
             shortcut_editor_rows: Vec::new(),
+            shortcut_capture_row: None,
+            shortcut_pending_add: false,
+            shortcut_reset_confirm: false,
+            shortcut_close_confirm: false,
             // Command aliases (populated from ocad.pgp just after construction)
             command_aliases: rustc_hash::FxHashMap::default(),
             alias_editor_rows: Vec::new(),