feat: add combo mode with combo counter, score and escalating effects

A 'Combo mode' toggle turns the display into a game-style counter.
Chords containing a modifier (Super/Ctrl/Alt/Shift/Menu/AltGr) are
combos: they build a combo counter, apply a multiplier (x2 at 5, x3 at
10 ... x8 at 50) and escalate the effects. Plain characters and shifted
chars typed alone are hits: +10 score only, they never touch the combo
counter or its window. Scoring: hit = 10, combo = (20 + 15*(mods-1) +
5*(keys-1)) * multiplier.

Counted once per physical chord on the Lua's empty payload (release),
so the intermediate growing emits of a chord never double-count. The
banner (COMBO 12 x3 - 3,450) sits below the history for bottom
positions and above it for top positions, with a floating +N pop per
press. Effects scale with modifiers and chain length: banner pulse,
hue shift, screen shake (up to 5px), continuous hue cycling at 10+
combos and a constant subtle vibration at 20+. The combo resets after
comboWindowMs (2s) without a new combo; the score accumulates for the
shell session.

Also fixes the README Behavior section: the history bullet was never
applied (a failed multi-edit call), now restored alongside the combo
mode docs. Manifest bumped to 1.7.0.

Panel.qml

@@ -29,6 +29,7 @@ Panel {
   property int margin: 67
   property int lingerMs: 1000
   property int historyCount: 1
+  property bool comboMode: false
 
   // Config lives outside the plugin folder (the shell reloads all plugin
   // code on any file change under ~/.config/omarchy/plugins/), so editing it
@@ -76,6 +77,7 @@ Panel {
     if (isFinite(cfg.margin) && cfg.margin >= 0) root.margin = Math.round(cfg.margin)
     if (isFinite(cfg.lingerMs) && cfg.lingerMs >= 0) root.lingerMs = Math.round(cfg.lingerMs)
     if (isFinite(cfg.historyCount)) root.historyCount = Math.max(1, Math.min(5, Math.round(cfg.historyCount)))
+    root.comboMode = cfg.comboMode === true
   }
 
   // Round-trips every option so a menu edit never drops values the display
@@ -86,12 +88,14 @@ Panel {
       position: root.position,
       margin: root.margin,
       lingerMs: root.lingerMs,
-      historyCount: root.historyCount
+      historyCount: root.historyCount,
+      comboMode: root.comboMode
     }
     for (var k in update) cfg[k] = update[k]
     if (update.mode !== undefined) root.mode = update.mode
     if (update.position !== undefined) root.position = update.position
     if (update.historyCount !== undefined) root.historyCount = update.historyCount
+    if (update.comboMode !== undefined) root.comboMode = update.comboMode
     writeProc.command = ["sh", "-c",
       "printf '%s\\n' '" + JSON.stringify(cfg) + "' > " + Util.shellQuote(root.configPath)]
     writeProc.running = true
@@ -168,6 +172,34 @@ Panel {
         }
       }
 
+      // Combo mode -----------------------------------------------------
+      // Game mode: combo counter + score with escalating effects (pulse,
+      // hue, screen shake). Chords with modifiers build the combo; plain
+      // characters are hits that only add score.
+      Item {
+        width: parent.width
+        height: comboSwitch.implicitHeight
+
+        Text {
+          anchors.left: parent.left
+          anchors.verticalCenter: parent.verticalCenter
+          text: "Combo mode"
+          font.family: Style.font.family
+          font.pixelSize: Style.font.body
+          color: Color.popups.text
+        }
+
+        ToggleSwitch {
+          id: comboSwitch
+          anchors.right: parent.right
+          anchors.verticalCenter: parent.verticalCenter
+          checked: root.comboMode
+          foreground: Color.popups.text
+          accent: Color.accent
+          onToggled: root.writeConfig({ comboMode: !root.comboMode })
+        }
+      }
+
       // Mode ----------------------------------------------------------
       Item {
         width: parent.width