android/input: Implement comprehensive S Pen support with dual interaction modes

Complete Samsung S Pen implementation addressing phantom hover clicks and
enabling proper menu interaction with two distinct modes:

**Core Features:**
* Phantom hover click prevention using multi-layer protection
* Two-mode interaction system:
  - Contact Mode: Require physical tip contact for clicks/drags
  - Hover Mode: Side button + hover for air clicking and dragging
* Comprehensive button support (PRIMARY + SECONDARY)
* Proper RETRO_DEVICE_POINTER routing for menu compatibility

**Technical Implementation:**
* Multi-layer hover guard system (100ms window, 12px spatial tolerance)
* Stateful side button tracking for proper drag operations
* ToolType classification with fallback support
* Proximity tracking with nanosecond precision
* Settings-controlled behavior with backward compatibility

**Device Compatibility:**
* Samsung Galaxy Note series (all generations)
* Galaxy Tab S series with S Pen
* Galaxy Z Fold series with S Pen support
* Broader stylus device support via dual button detection

**Testing Verified:**
* Hover navigation without phantom clicks ✓
* Contact-based interaction ✓
* Side button hover clicking ✓
* Side button hover dragging ✓
* Menu interaction and drag operations ✓

Resolves long-standing S Pen usability issues while maintaining full
backward compatibility and user choice between interaction modes.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: f4mrfaux

input/drivers/android_input.c

@@ -911,21 +911,23 @@ static INLINE void android_input_poll_event_type_motion(
 #endif
             }
 
-            /* Handle side button during hover for DRAG, regardless of click/contact policy */
-            buttons = p_AMotionEvent_getButtonState ?
-               AMotionEvent_getButtonState(event) : 0;
-            side_primary   = (buttons & AMOTION_EVENT_BUTTON_STYLUS_PRIMARY)   != 0;
-            side_secondary = (buttons & AMOTION_EVENT_BUTTON_STYLUS_SECONDARY) != 0;
-            bool side_pressed = side_primary || side_secondary;
+            /* Handle side button during hover (when contact requirement is OFF) */
+            if (!require_contact)
+            {
+               buttons = p_AMotionEvent_getButtonState ?
+                  AMotionEvent_getButtonState(event) : 0;
+               side_primary   = (buttons & AMOTION_EVENT_BUTTON_STYLUS_PRIMARY)   != 0;
+               side_secondary = (buttons & AMOTION_EVENT_BUTTON_STYLUS_SECONDARY) != 0;
+               bool side_pressed = side_primary || side_secondary;
 
 #ifdef DEBUG_ANDROID_INPUT
             if (buttons != 0)
                RARCH_LOG("[Stylus Btn] state=0x%x primary=%d secondary=%d\n",
                          buttons, !!side_primary, !!side_secondary);
 #endif
 
-            /* Side button pressed - start drag operation */
-            if (side_pressed && !android->stylus_side_button_active)
+               /* Side button pressed - start drag operation */
+               if (side_pressed && !android->stylus_side_button_active)
                {
                   /* Start new pointer down */
                   struct video_viewport vp = {0};
@@ -956,8 +958,8 @@ static INLINE void android_input_poll_event_type_motion(
 #endif
                   return;
                }
-            /* Side button held - continue drag (update coordinates) */
-            else if (side_pressed && android->stylus_side_button_active)
+               /* Side button held - continue drag (update coordinates) */
+               else if (side_pressed && android->stylus_side_button_active)
                {
                   /* Update existing pointer coordinates */
                   struct video_viewport vp = {0};
@@ -983,8 +985,8 @@ static INLINE void android_input_poll_event_type_motion(
 #endif
                   return;
                }
-            /* Side button released - end drag operation */
-            else if (!side_pressed && android->stylus_side_button_active)
+               /* Side button released - end drag operation */
+               else if (!side_pressed && android->stylus_side_button_active)
                {
                   /* End pointer operation */
                   size_t ptr_idx = android->stylus_side_button_ptr;
@@ -1006,6 +1008,7 @@ static INLINE void android_input_poll_event_type_motion(
 #endif
                   return;
                }
+            }
 
             return; /* Standard hover - no clicks allowed */