refactor(cmd): introduce command algebra with Binding::Sequence and unified primitives

Add Binding::Sequence to keymap for composing commands, then use it
and parameterization to eliminate redundant command structs:

- Unify MoveSelection/JumpToEdge/ScrollRows/PageScroll into Move
- Merge ToggleGroupUnderCursor + ToggleColGroupUnderCursor → ToggleGroupAtCursor
- Merge CommitCellEdit + CommitAndAdvanceRight → CommitAndAdvance
- Merge CycleAxisForTile + SetAxisForTile → TileAxisOp
- Merge ViewBackCmd + ViewForwardCmd → ViewNavigate
- Delete SearchAppendChar/SearchPopChar (reuse AppendChar/PopChar with "search")
- Replace SaveAndQuit/OpenRecordRow with keymap sequences
- Extract commit_add_from_buffer helper for CommitCategoryAdd/CommitItemAdd
- Add algebraic law tests (idempotence, involution, associativity)

https://claude.ai/code/session_01Y9X6VKyZAW3xo1nfThDRYU

src/command/keymap.rs

@@ -72,6 +72,8 @@ pub enum Binding {
     },
     /// A prefix sub-keymap (Emacs-style).
     Prefix(Arc<Keymap>),
+    /// A sequence of commands executed in order, concatenating their effects.
+    Sequence(Vec<(&'static str, Vec<String>)>),
 }
 
 /// A keymap maps key patterns to bindings (command names or prefix sub-keymaps).
@@ -121,6 +123,17 @@ impl Keymap {
             .insert(KeyPattern::Key(key, mods), Binding::Prefix(sub));
     }
 
+    /// Bind a key to a sequence of commands (executed in order).
+    pub fn bind_seq(
+        &mut self,
+        key: KeyCode,
+        mods: KeyModifiers,
+        steps: Vec<(&'static str, Vec<String>)>,
+    ) {
+        self.bindings
+            .insert(KeyPattern::Key(key, mods), Binding::Sequence(steps));
+    }
+
     /// Bind a catch-all for any Char key.
     pub fn bind_any_char(&mut self, name: &'static str, args: Vec<String>) {
         self.bindings
@@ -173,6 +186,14 @@ impl Keymap {
                 Some(cmd.execute(ctx))
             }
             Binding::Prefix(sub) => Some(vec![Box::new(SetTransientKeymap(sub.clone()))]),
+            Binding::Sequence(steps) => {
+                let mut effects: Vec<Box<dyn Effect>> = Vec::new();
+                for (name, args) in steps {
+                    let cmd = registry.interactive(name, args, ctx).ok()?;
+                    effects.extend(cmd.execute(ctx));
+                }
+                Some(effects)
+            }
         }
     }
 }
@@ -360,7 +381,14 @@ impl KeymapSet {
         // Drill into aggregated cell / view history / add row
         normal.bind(KeyCode::Char('>'), none, "drill-into-cell");
         normal.bind(KeyCode::Char('<'), none, "view-back");
-        normal.bind(KeyCode::Char('o'), none, "open-record-row");
+        normal.bind_seq(
+            KeyCode::Char('o'),
+            none,
+            vec![
+                ("add-record-row", vec![]),
+                ("enter-edit-at-cursor", vec![]),
+            ],
+        );
 
         // Records mode toggle and prune toggle
         normal.bind(KeyCode::Char('R'), none, "toggle-records-mode");
@@ -384,7 +412,11 @@ impl KeymapSet {
         normal.bind_prefix(KeyCode::Char('y'), none, Arc::new(y_map));
 
         let mut z_map = Keymap::new();
-        z_map.bind(KeyCode::Char('Z'), none, "save-and-quit");
+        z_map.bind_seq(
+            KeyCode::Char('Z'),
+            none,
+            vec![("save", vec![]), ("force-quit", vec![])],
+        );
         normal.bind_prefix(KeyCode::Char('Z'), none, Arc::new(z_map));
 
         set.insert(ModeKey::Normal, Arc::new(normal));
@@ -664,8 +696,13 @@ impl KeymapSet {
         let mut sm = Keymap::new();
         sm.bind(KeyCode::Esc, none, "exit-search-mode");
         sm.bind(KeyCode::Enter, none, "exit-search-mode");
-        sm.bind(KeyCode::Backspace, none, "search-pop-char");
-        sm.bind_any_char("search-append-char", vec![]);
+        sm.bind_args(
+            KeyCode::Backspace,
+            none,
+            "pop-char",
+            vec!["search".into()],
+        );
+        sm.bind_any_char("append-char", vec!["search".into()]);
         set.insert(ModeKey::SearchMode, Arc::new(sm));
 
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