Fix concurrency, detached document, and permissions checks in algorithms.

[markafoltz]

• Eliminate a redundant check for an aborted signal.
• Add a note about locking for the tool map before it's shown to the browser agent.
• Add a check for a detached document before allowing a tool call on it.
• Separate out steps to enumerate tools, from constructing RegisteredTools, as parse a JSON string cannot happen in parallel.
  • Maybe there's a different / cleaner way to handle this? But I think the parallel steps have to complete first outside of any script context, as they traverse the frame tree.

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