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

[markafoltz]

• Eliminate a redundant check for an aborted signal.
• In tool enumeration, skip frames that don't have the tools permission.
• 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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[domfarolino]

I think we can omit |targetOrigin| since that's already captured by |targetDocument|'s [=Document/origin=] right?

[markafoltz]

I wonder if |targetOrigin| can change between the capture here and the task below that iterates over |discoveredTools|.

[domfarolino]

Hmm, I suppose this isn't strictly necessary since a document without this feature cannot even populate tools in its internal context's tool map accessed below, right?

I guess it's good documentation for an agent though. Does my assessment above match your understanding?

[markafoltz]

The perform and observation algorithm can be triggered at any time. If the spec can guarantee that the tool map is always synchronized with the state of the tools permission, then this can be skipped. But it's also fine to leave in as documentation. Let me know what you think.