feat: configurable force-press (alt-character) threshold

Sources/TouchpadInputApp/Views/SettingsPanel.swift

@@ -17,6 +17,10 @@ struct SettingsPanel: View {
                        value: String(format: "%.2f", session.pressureFloor)) {
                 Slider(value: $session.pressureFloor, in: 0.05...0.50, step: 0.05)
             }
+            settingRow(label: "Force-press threshold",
+                       value: String(format: "%.2f", session.forcePressThreshold)) {
+                Slider(value: $session.forcePressThreshold, in: 0.70...1.00, step: 0.05)
+            }
             settingRow(label: "Min contact size",
                        value: String(format: "%.2f", session.minContactSize)) {
                 Slider(value: $session.minContactSize, in: 0.0...1.0, step: 0.05)

Sources/TouchpadInputCore/DefaultImplementations/CharacterEmitter.swift

@@ -12,13 +12,14 @@ public struct CharacterEmitter: CharacterResolver {
     // MARK: CharacterResolver
 
     public func character(forZoneID id: String, pressure: Float,
-                          modifiers: Set<AnyModifierKind>, pressureFloor: Float) -> Character? {
+                          modifiers: Set<AnyModifierKind>, pressureFloor: Float,
+                          forcePressThreshold: Float = 0.95) -> Character? {
         guard pressure >= pressureFloor else { return nil }
         guard let zone = grid.zones.first(where: { String($0.character) == id }) else { return nil }
         if modifiers.contains(.shift) {
             return Character(String(zone.character).uppercased())
         }
-        return resolve(zone: zone, pressure: pressure)
+        return resolve(zone: zone, pressure: pressure, forcePressThreshold: forcePressThreshold)
     }
 
     // MARK: Legacy coordinate-based API (kept for direct-use tests)
@@ -27,13 +28,13 @@ public struct CharacterEmitter: CharacterResolver {
                                   pressure: Float, pressureFloor: Float = 0.30) -> Character? {
         guard pressure >= pressureFloor else { return nil }
         guard let zone = grid.zone(at: x, y: y) else { return nil }
-        return resolve(zone: zone, pressure: pressure)
+        return resolve(zone: zone, pressure: pressure, forcePressThreshold: 0.95)
     }
 
     // MARK: Private
 
-    private func resolve(zone: KeyZone, pressure: Float) -> Character {
-        if pressure >= 0.95 {
+    private func resolve(zone: KeyZone, pressure: Float, forcePressThreshold: Float) -> Character {
+        if pressure >= forcePressThreshold {
             return zone.altCharacter ?? Character(String(zone.character).uppercased())
         } else {
             return zone.character

Sources/TouchpadInputCore/Protocols/CharacterResolver.swift

@@ -4,5 +4,6 @@
 public protocol CharacterResolver: Sendable {
     /// Returns the character for the given zone and pressure level, or nil if no character should be emitted.
     func character(forZoneID id: String, pressure: Float,
-                   modifiers: Set<AnyModifierKind>, pressureFloor: Float) -> Character?
+                   modifiers: Set<AnyModifierKind>, pressureFloor: Float,
+                   forcePressThreshold: Float) -> Character?
 }

Sources/TouchpadInputCore/Session/TouchInputSession.swift

@@ -60,6 +60,7 @@ public final class TouchInputSession: ObservableObject, @preconcurrency TouchEve
     // MARK: Stability settings
 
     @Published public var pressureFloor: Float = 0.30
+    @Published public var forcePressThreshold: Float = 0.95
     @Published public var minContactSize: Float = 0.0
     @Published public var zoneCooldownMs: Double = 80.0
 
@@ -308,7 +309,8 @@ public final class TouchInputSession: ObservableObject, @preconcurrency TouchEve
                                         forZoneID: zoneID,
                                         pressure: effectivePressure,
                                         modifiers: heldModifiers,
-                                        pressureFloor: pressureFloor
+                                        pressureFloor: pressureFloor,
+                                        forcePressThreshold: forcePressThreshold
                                     ) {
                                         outputBuffer.append(ch)
                                         externalOutputTarget?.emit(character: ch)