vaxis: implement osc9 and osc777 notifications

Signed-off-by: Tim Culverhouse <[e-mail]>

README.md

···
 | Styled Underlines              |  ✅   |    ✅    |    ✅     |
 | Mouse Shapes (OSC 22)          |  ✅   | planned  |    ❌     |
 | System Clipboard (OSC 52)      |  ✅   | planned  |    ❌     |
-| System Notifications (OSC 9)   |  ✅   | planned  |    ❌     |
-| System Notifications (OSC 777) |  ✅   | planned  |    ❌     |
+| System Notifications (OSC 9)   |  ✅   |    ✅    |    ❌     |
+| System Notifications (OSC 777) |  ✅   |    ✅    |    ❌     |
 | Synchronized Output (DEC 2026) |  ✅   |    ✅    |    ✅     |
 | Unicode Core (DEC 2027)        |  ✅   |    ✅    |    ❌     |
 | Color Mode Updates (DEC 2031)  |  ✅   | planned  |    ❌     |

examples/text_input.zig

···
                     break :outer;
                 } else if (key.matches('l', .{ .ctrl = true })) {
                     vx.queueRefresh();
+                } else if (key.matches('n', .{ .ctrl = true })) {
+                    try vx.notify("vaxis", "hello from vaxis");
                 } else {
                     try text_input.update(.{ .key_press = key });
                 }

src/cell.zig

···
     bg: Color = .default,
     ul: Color = .default,
     ul_style: Underline = .off,
+    // TODO: url should maybe go outside of style. We'll need to allocate these
+    // in the internal screen
     url: ?[]const u8 = null,
     url_params: ?[]const u8 = null,
 

src/ctlseqs.zig

···
 // OSC sequences
 pub const osc8 = "\x1b]8;{s};{s}\x1b\\";
 pub const osc8_clear = "\x1b]8;;\x1b\\";
+pub const osc9_notify = "\x1b]9;{s}\x1b\\";
+pub const osc777_notify = "\x1b]777;notify;{s};{s}\x1b\\";

src/vaxis.zig

···
             );
             try self.tty.?.flush();
         }
+
+        /// send a system notification
+        pub fn notify(self: *Self, title: ?[]const u8, body: []const u8) !void {
+            if (self.tty == null) return;
+            if (title) |t| {
+                try std.fmt.format(
+                    self.tty.?.buffered_writer.writer(),
+                    ctlseqs.osc777_notify,
+                    .{ t, body },
+                );
+            } else {
+                try std.fmt.format(
+                    self.tty.?.buffered_writer.writer(),
+                    ctlseqs.osc9_notify,
+                    .{body},
+                );
+            }
+        }
     };
 }