terminal: OSC 133 B handling

src/terminal/Terminal.zig

@@ -1070,6 +1070,7 @@ pub fn semanticPrompt(
 ) !void {
     switch (cmd.action) {
         .fresh_line => try self.semanticPromptFreshLine(),
+
         .fresh_line_new_prompt => {
             // "First do a fresh-line."
             try self.semanticPromptFreshLine();
@@ -1092,6 +1093,12 @@ pub fn semanticPrompt(
             // command but we don't yet handle these in any meaningful way.
         },
 
+        .end_prompt_start_input => {
+            // End of prompt and start of user input, terminated by a OSC
+            // "133;C" or another prompt (OSC "133;P").
+            self.screens.active.cursor.semantic_content = .input;
+        },
+
         else => {},
     }
 }

src/terminal/stream_readonly.zig

@@ -933,3 +933,18 @@ test "semantic prompt fresh line new prompt" {
     try s.nextSlice("\x1b]133;A;redraw=1\x07");
     try testing.expect(t.flags.shell_redraws_prompt);
 }
+
+test "semantic prompt end prompt start input" {
+    var t: Terminal = try .init(testing.allocator, .{ .cols = 10, .rows = 10 });
+    defer t.deinit(testing.allocator);
+
+    var s: Stream = .initAlloc(testing.allocator, .init(&t));
+    defer s.deinit();
+
+    // Write some text and then send OSC 133;A (fresh_line_new_prompt)
+    try s.nextSlice("Hello");
+    try s.nextSlice("\x1b]133;A\x07");
+    try s.nextSlice("prompt$ ");
+    try s.nextSlice("\x1b]133;B\x07");
+    try testing.expectEqual(.input, t.screens.active.cursor.semantic_content);
+}