refactor: rename pty_process to cc_runner

The module has long since moved away from PTY technology, using
claude -p with --output-format stream-json and --resume instead.
Rename to cc_runner to accurately reflect what it does.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

tests/conftest.py

@@ -51,7 +51,7 @@ def mock_run_claude():
     Default return value is a short CC-style output string.
     """
     mock = AsyncMock(return_value="Claude Code: task complete.")
-    with patch("agent.pty_process.run_claude", mock), \
+    with patch("agent.cc_runner.run_claude", mock), \
          patch("agent.manager.run_claude", mock):
         yield mock