Clarify touch gesture and input API comments

Simplify and clarify documentation for touch gesture detection (back gesture, item taps, long-press) and board detection flags. No functional changes, just improved comment readability.

src/activities/home/HomeActivity.cpp

@@ -179,12 +179,9 @@ void HomeActivity::loop() {
     requestUpdate();
   });
 
-  // A tap on a menu button selects + activates it. The button menu registers
-  // menu-local ids (it is drawn with selectorIndex offset by recentBooks.size()),
-  // so map the tapped id back into the global selector space. (The recent-book
-  // cover is a separate, single-item draw path — tappable in a later phase.)
-  // Touch-down moves the selector to the pressed menu button (shows selected state),
-  // like Up/Down; release opens it below.
+  // Tap a menu button to select + activate it. The button menu registers
+  // menu-local ids (drawn with selectorIndex offset by recentBooks.size()), so map
+  // back into the global selector space. Touch-down shows it selected; release opens.
   int downId = -1;
   if (mappedInput.wasItemTouchedDown(downId)) {
     selectorIndex = static_cast<int>(recentBooks.size()) + downId;

src/activities/reader/EpubReaderActivity.cpp

@@ -256,12 +256,8 @@ void EpubReaderActivity::loop() {
     requestUpdate();
   }
 
-  // Touch reader controls mirror the side page buttons (left third = back, right
-  // third = forward, press-and-hold = long-press behavior) and the Confirm
-  // button (center press-and-hold = open menu). The top-left Back corner is
-  // consumed by wasReleased(Back) earlier, so it never reaches here. No-op on
-  // Xteink / when the setting is off. wasTouchTap is idempotent within a frame,
-  // so reading it here and again below is safe.
+  // Touch page nav (idempotent within a frame, so read here and again below). The
+  // top-left Back corner is consumed by wasReleased(Back) above, never reaching here.
   const auto touch = ReaderUtils::detectTouchPageTurn(renderer);
 
   // Enter reader menu activity (Confirm release, or a center touch-and-hold).

src/activities/reader/ReaderUtils.h

@@ -65,14 +65,10 @@ inline PageTurnResult detectPageTurn(const MappedInputManager& input) {
   return {prev, next, tiltPrev || tiltNext};
 }
 
-// Touch reader controls: a tap on the left third of the (oriented) screen turns
-// back a page, the right third turns forward, mirroring the side page buttons.
-// The center third opens the reader menu on press-and-hold (see center/heldMs;
-// the menu/Back gesture is handled by each reader). heldMs carries the contact
-// duration so callers can apply the same long-press behavior (chapter skip /
-// orientation change) as the buttons. Gated off the Xteink devices (no touch)
-// and behind the touchReaderControls setting; returns all-false otherwise, so
-// non-touch readers pay a single branch.
+// Touch reader controls: left third = page back, right third = forward, center =
+// open menu on press-and-hold (see isTouchMenuGesture). heldMs is the contact
+// duration, for the same long-press behavior as the buttons (chapter skip).
+// All-false on Xteink (no touch) or when the setting is off.
 struct TouchPageTurn {
   bool prev;
   bool next;

src/activities/reader/TxtReaderActivity.cpp

@@ -72,8 +72,7 @@ void TxtReaderActivity::loop() {
     return;
   }
 
-  // Touch reader controls mirror the side page buttons (left third = back,
-  // right third = forward). No-op on Xteink / when the setting is off.
+  // Touch page nav (left third = back, right third = forward).
   const auto touch = ReaderUtils::detectTouchPageTurn(renderer);
 
   auto [prevTriggered, nextTriggered, fromTilt] = ReaderUtils::detectPageTurn(mappedInput);

src/activities/reader/XtcReaderActivity.cpp

@@ -53,10 +53,7 @@ void XtcReaderActivity::onExit() {
 }
 
 void XtcReaderActivity::loop() {
-  // Touch reader controls mirror the side page buttons (left third = back, right
-  // third = forward, press-and-hold = chapter skip) and the Confirm button
-  // (center press-and-hold = chapter selection). No-op on Xteink / when the
-  // setting is off.
+  // Touch page nav; center hold opens chapter selection (the Confirm analogue).
   const auto touch = ReaderUtils::detectTouchPageTurn(renderer);
 
   // Enter chapter selection activity (Confirm release, or a center touch-and-hold).

src/activities/settings/SettingsActivity.cpp

@@ -115,11 +115,9 @@ void SettingsActivity::onExit() {
 void SettingsActivity::loop() {
   bool hasChangedCategory = false;
 
-  // A tap on a settings row selects + activates it in one gesture. The list is drawn
-  // with selectedIndex = selectedSettingIndex - 1 (row 0 is the category tab), so map
-  // the tapped 0-based row back by +1. (Category tab bar is tappable in a later phase.)
-  // Touch-down moves the selection to the pressed row (shows selected state); release
-  // toggles/activates it below. (Row 0 is the tab bar, so settings list id 0 -> index 1.)
+  // Tap a settings row to select + activate it. Row 0 is the tab bar, so the list
+  // is drawn at selectedSettingIndex - 1; map the tapped row back by +1. Touch-down
+  // shows it selected; release toggles/activates below.
   int downId = -1;
   if (mappedInput.wasItemTouchedDown(downId) && downId >= 0 && downId < settingsCount) {
     selectedSettingIndex = downId + 1;

src/activities/util/KeyboardEntryActivity.cpp

@@ -337,11 +337,9 @@ void KeyboardEntryActivity::loop() {
     }
   }
 
-  // A tap selects the key and presses it. Encoded id = row*100+col (bottom function
-  // row = getContentRowCount()). A touch-and-hold inserts the alternate character
-  // (numbers/symbols on a letter), mirroring the button long-press — wasItemLongPressed
-  // is checked first since it's a subset of wasItemTapped's releases. Skipped in
-  // cursor mode, where a tap on a key would be ambiguous with cursor editing.
+  // Tap a key to press it (encoded id = row*100+col). Touch-and-hold inserts the
+  // alternate char, like the button long-press (check wasItemLongPressed first, it's
+  // a subset of these releases). Skipped in cursor mode (ambiguous with editing).
   int tappedKey = -1;
   if (!cursorMode && mappedInput.wasItemTapped(tappedKey)) {
     selectedRow = tappedKey / 100;