terminal: store title set by escape sequences

Add a title field to Terminal, mirroring the existing pwd field.
The title is set via setTitle/getTitle and tracks the most recent
value written by OSC 0/2 sequences. The stream handler now persists
the title in terminal state in addition to forwarding it to the
surface. The field is cleared on full reset.

src/terminal/Terminal.zig

@@ -67,6 +67,9 @@ scrolling_region: ScrollingRegion,
 /// The last reported pwd, if any.
 pwd: std.ArrayList(u8),
 
+/// The title of the terminal as set by escape sequences (e.g. OSC 0/2).
+title: std.ArrayList(u8),
+
 /// The color state for this terminal.
 colors: Colors,
 
@@ -219,6 +222,7 @@ pub fn init(
             .right = cols - 1,
         },
         .pwd = .empty,
+        .title = .empty,
         .colors = opts.colors,
         .modes = .{
             .values = opts.default_modes,
@@ -231,6 +235,7 @@ pub fn deinit(self: *Terminal, alloc: Allocator) void {
     self.tabstops.deinit(alloc);
     self.screens.deinit(alloc);
     self.pwd.deinit(alloc);
+    self.title.deinit(alloc);
     self.* = undefined;
 }
 
@@ -2881,6 +2886,19 @@ pub fn getPwd(self: *const Terminal) ?[]const u8 {
     return self.pwd.items;
 }
 
+/// Set the title for the terminal, as set by escape sequences (e.g. OSC 0/2).
+pub fn setTitle(self: *Terminal, t: []const u8) !void {
+    self.title.clearRetainingCapacity();
+    try self.title.appendSlice(self.gpa(), t);
+}
+
+/// Returns the title for the terminal, if any. The memory is owned by the
+/// Terminal and is not copied. It is safe until a reset or setTitle.
+pub fn getTitle(self: *const Terminal) ?[]const u8 {
+    if (self.title.items.len == 0) return null;
+    return self.title.items;
+}
+
 /// Switch to the given screen type (alternate or primary).
 ///
 /// This does NOT handle behaviors such as clearing the screen,
@@ -3090,6 +3108,7 @@ pub fn fullReset(self: *Terminal) void {
     self.tabstops.reset(TABSTOP_INTERVAL);
     self.previous_char = null;
     self.pwd.clearRetainingCapacity();
+    self.title.clearRetainingCapacity();
     self.status_display = .main;
     self.scrolling_region = .{
         .top = 0,

src/termio/stream_handler.zig

@@ -999,6 +999,12 @@ pub const StreamHandler = struct {
             return;
         }
 
+        // Set the title on the terminal state. We ignore any errors since
+        // we can continue to operate just fine without it.
+        self.terminal.setTitle(title) catch |err| {
+            log.warn("error setting title in terminal state: {e}", .{err});
+        };
+
         @memcpy(buf[0..title.len], title);
         buf[title.len] = 0;