feat: only autoscroll Continue console when focused on last element

[fbricon]

Description

While the Continue console is adding content during an LLM response, it's impossible to scroll back up because scrolling is locked to the last item. This PR allows the user to scroll back up, which automatically suspends autoscroll. It resumes when scrolling back to the last item

cc @owtaylor

Checklist

• I've read the contributing guide
• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

Screenshots

smarter-console-autoscroll.mp4

Tests

Manual testing (see video)

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Summary by mrge

The Continue console now only autoscrolls when you are focused on the last item, letting you scroll up and pause autoscroll during LLM responses.

• New Features
  • Autoscroll suspends when you scroll up and resumes when you return to the bottom.

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[RomneyDa]

Nice fix for console scrolling