activeShellCommandLine

Returns the active shell command-line snapshot, when OSC 133 prompt markers provide a trustworthy visible range.

The read is serialized with parser/core mutation and reconstructs text from the current render frame using the same prompt-end marker state used for completed command capture. null means the shell has not reported a prompt-end marker, the cursor is not at the visible command end, the command exceeds the bounded extraction limits, or no command is currently being edited.