Queued-command task delivery gains richer turn/position tracking

What

• The dedup/merge helper that delivers queued-command notifications into the transcript now takes a structured options object ({startsTurn, inDrainPosition, inHumanTurn}) instead of positional booleans, used for both taskDelivery on user messages and queued_command attachments.
• The bash-task-delivery splicing logic now distinguishes a third structural outcome, after_turn, in addition to the existing append/new_turn, based on new position parameters; it's recorded in the tengu_bash_task_delivered telemetry event.
• The logic that decides whether a message counts as a completed tool-result turn (for grouping/rendering) now also treats user messages carrying a taskDelivery field as qualifying, not just ones with tool_result content.
• The check for whether a message counts toward rewind/history segmentation likewise now treats messages with a taskDelivery field as eligible, not just tool_result-bearing ones.

Why These changes make messages that deliver queued command results behave consistently with normal tool-result messages for turn grouping, rewind/history, and telemetry, instead of being treated as a special case that could be miscounted or misplaced.