GetTask tool for background task results, behind the tengu_violin_rosin flag

What

GetTask is a tool Claude can use to check on a background shell command by its task ID. A background shell command is one Claude started that keeps running while the conversation goes on. The tool returns the task's state, in the same shape as the MCP tasks interface. Before, GetTask was always turned off in the code. Now it depends on a remote flag.

• The tool is available, and listed among the tools Claude can load on demand, only when the remote flag tengu_violin_rosin is on and three other conditions hold. With no value from the server the flag falls back to off, so the tool stays hidden.
• When the tool is on, Claude Code itself inserts a GetTask call when a background task finishes. The finished task is then delivered as a GetTask result rather than a plain notification. This is why the tool's description says Claude Code usually calls it on Claude's behalf.
• If Claude calls GetTask again on the same task within one response, it gets an error instead of a second answer.
• The same flag check decides whether a killed background Bash task that is not a monitor is saved with the outcome "killed". It also controls some new tracking in the PowerShell tool.
• Results show as one dim status line, such as "completed with errors" or "<N> chars of output". "still running" appears only in verbose or transcript mode. A repeated call shows nothing outside verbose mode.

Why

This changes how results from background commands reach Claude once the flag is on. Until then, nothing changes for you.