core: avoid possible deadlock in right-click-action paste actions

Fixes #8313

The clipboard request flow can result in the apprt immediately
completing the request which itself grabs a lock. For pastes, we should
yield the lock during the clipboard request.

GTK is always async so this worked there, but we want to be resilient to
any apprt behavior here.

src/Surface.zig

@@ -3555,26 +3555,7 @@ pub fn mouseButtonCallback(
         };
 
         switch (self.config.right_click_action) {
-            .ignore => {
+            .ignore => {},
-                // Return early to skip clearing the selection.
-                try self.queueRender();
-                return true;
-            },
-            .copy => {
-                if (self.io.terminal.screen.selection) |sel| {
-                    self.copySelectionToClipboards(sel, &.{.standard});
-                }
-            },
-            .@"copy-or-paste" => {
-                if (self.io.terminal.screen.selection) |sel| {
-                    self.copySelectionToClipboards(sel, &.{.standard});
-                } else {
-                    try self.startClipboardRequest(.standard, .paste);
-                }
-            },
-            .paste => {
-                try self.startClipboardRequest(.standard, .paste);
-            },
             .@"context-menu" => {
                 // If we already have a selection and the selection contains
                 // where we clicked then we don't want to modify the selection.
@@ -3588,12 +3569,45 @@ pub fn mouseButtonCallback(
                 const sel = screen.selectWord(pin) orelse break :sel;
                 try self.setSelection(sel);
                 try self.queueRender();
+
+                // Don't consume so that we show the context menu in apprt.
                 return false;
             },
-        }
+            .copy => {
+                if (self.io.terminal.screen.selection) |sel| {
+                    self.copySelectionToClipboards(sel, &.{.standard});
+                }
 
-        try self.setSelection(null);
+                try self.setSelection(null);
-        try self.queueRender();
+                try self.queueRender();
+            },
+            .@"copy-or-paste" => if (self.io.terminal.screen.selection) |sel| {
+                self.copySelectionToClipboards(sel, &.{.standard});
+                try self.setSelection(null);
+                try self.queueRender();
+            } else {
+                // Pasting can trigger a lock grab in complete clipboard
+                // request so we need to unlock.
+                self.renderer_state.mutex.unlock();
+                defer self.renderer_state.mutex.lock();
+                try self.startClipboardRequest(.standard, .paste);
+
+                // We don't need to clear selection because we didn't have
+                // one to begin with.
+            },
+            .paste => {
+                // Before we yield the lock, clear our selection if we have
+                // one.
+                try self.setSelection(null);
+                try self.queueRender();
+
+                // Pasting can trigger a lock grab in complete clipboard
+                // request so we need to unlock.
+                self.renderer_state.mutex.unlock();
+                defer self.renderer_state.mutex.lock();
+                try self.startClipboardRequest(.standard, .paste);
+            },
+        }
 
         // Consume the event such that the context menu is not displayed.
         return true;