Preserve selected message in inspector on updates

[adranjan4]

Summary

• Fixes inspector overrides user's selected message on update #247: inspector no longer steals selection when new LSP messages arrive
• Auto-follows the latest row only when the cursor is already on the last message
• Applies to both lsp-devtools inspect and the client inspector

Test plan

• cd lib/lsp-devtools && hatch test (or pytest on tests/inspector/test_message_browser.py)
• Run lsp-devtools inspect, feed chatty traffic, select a middle row — selection should stick
• Move to the last row — new messages should still follow the tail

[adranjan4]

pre-commit.ci is failing with the same ruff/mypy issues present on develop (not introduced here). Happy to help clean those up in a follow-up if needed.

[alcarney]

Thanks for opening this!

pre-commit.ci is failing with the same ruff/mypy issues present on develop

Yeah, it's a sign that the code is relatively immature still, happy to ignore any existing errors for now.

I've not had chance to try the branch out myself yet, but the implementation looks good. If you're adding tests though, I'd prefer it them to use a SqlHandler instance with an in-memory db connection, rather than having to maintain a separate _FakeDb implementation.

[adranjan4]

Thanks for the review! Updated the tests to use SqlHandler(":memory:") instead of _FakeDb.

[alcarney]

Thanks! I've finally had a chance to try it out and can confirm it works as expected 😄