Stop now actually stops a running tool call

Pressing Stop while an agent was in the middle of a mesh operation — reading a node, searching, patching, moving, or running a code check — did not stop it. The button ended the round on screen while the operation kept running underneath, so the work carried on invisibly and the thread could take a long time to settle.

Every one of those tools now listens for the stop signal: get, search, create, update, patch, edit_content, delete, move, copy, get_diagnostics, recycle, navigate_to, run_tests, the four code-intelligence tools, and the agent's own working-files tools. Stop unwinds them straight away, and the work is torn down rather than merely abandoned.

Two smaller things came with it:

• A tool that fails now answers. A failure used to surface as a raw error; the agent now receives it as an ordinary result it can read, explain, and work around.
• A tool that comes back with nothing now says so — previously that case produced no answer at all, which is what left some rounds waiting indefinitely.