fix: use pyte terminal emulator for screenshot rendering

Replaces simple carriage return handling with pyte terminal emulator
to properly interpret all ANSI escape sequences including cursor
positioning. This fixes the tmux status bar 'creeping up' issue in
screenshots.

Adds pyte dependency to pyproject.toml.

Resolves TODO item #2.

tests/test_local_server_unit.py

@@ -111,8 +111,24 @@ class TestLocalServerHelpers:
     """Tests for LocalServer helper methods."""
 
     def test_apply_carriage_returns_overwrites_line(self):
-        text = "hello\rworld\nnext"
-        assert _apply_carriage_returns(text) == ["world", "next"]
+        text = "hello\rworld\r\nnext"
+        # pyte terminal emulator interprets CR properly - overwrites hello with world
+        lines = _apply_carriage_returns(text, width=80, height=24)
+        # First line should have "world" (overwritten), second line "next"
+        assert lines[0] == "world"
+        assert lines[1] == "next"
+
+    def test_apply_carriage_returns_handles_cursor_positioning(self):
+        # Simulate tmux-style cursor positioning to row 5, column 1 (\x1b[5;1H)
+        # Then clear to end of line (\x1b[K) and write new content
+        # Use \r\n for proper line endings
+        text = "line1\r\nline2\r\nline3\r\nline4\r\nline5\x1b[5;1H\x1b[Kupdated"
+        lines = _apply_carriage_returns(text, width=80, height=10)
+        # Line 5 (index 4) should be overwritten with "updated"
+        assert lines[4] == "updated"
+        # Previous lines should remain
+        assert lines[0] == "line1"
+        assert lines[1] == "line2"
 
     @pytest.mark.asyncio
     async def test_keyboard_interrupt_closes_sessions_and_websockets(self, server, monkeypatch):
@@ -755,7 +771,7 @@ class TestLocalServerMoreCoverage:
 
         captured = {"len": None}
 
-        def apply_cr(text: str):
+        def apply_cr(text: str, width: int = 80, height: int = 24):
             captured["len"] = len(text)
             return ["x"]