TaskOutput tool removed; task output is now read via the Read tool

What

• The TaskOutput tool has been removed. Its config field's description now says background task output should be read via the Read tool instead.
• TaskOutput was dropped from the internal tool set used alongside Read, Glob, Grep, NotebookRead, Skill, AskUserQuestion, TaskCreate, TaskGet, TaskList, TaskUpdate, TaskStop, Agent, and TodoWrite.
• The TASK_MAX_OUTPUT_LENGTH environment variable was dropped from the list of recognized/passthrough settings.
• The function that computes the maximum characters allowed for task output no longer reads a taskOutputMaxChars setting; it now derives the limit from the current output host/target instead.

Why

This consolidates reading background task output onto the Read tool instead of a separate TaskOutput tool, and moves the output-length limit from a fixed global setting to something derived from where the output is being read.