fix: windows can now paste non-ascii multiline text

[occurrent]

Fixes #2137

On Windows, Codex relies on PasteBurst for paste detection because
bracketed paste is not reliably available via crossterm.

When pasted content starts with non-ASCII characters, input is routed
through handle_non_ascii_char, which bypasses the normal paste burst
logic. This change extends the paste burst window for that path, which
should ensure that Enter is correctly grouped as part of the paste.

Adds a regression test:

• non_ascii_start_extends_burst_window_for_enter

[github-actions]

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[occurrent]

I have read the CLA Document and I hereby sign the CLA

[andromarces]

Hi @occurrent!

Why close this?

[occurrent]

@andromarces I found original patch introduced non ascii path could mis handle multibyte input, which could lead to panics or incorrect behavior when handling multibyte characters. This should heve been fixed in the latest commit.

[etraut-openai]

@occurrent, can you clarify the latest status of this PR? Does your most recent commit address the incorrect behavior that you noted in your comment above?

[occurrent]

@etraut-openai Yes, the most recent commit fixes the incorrect behavior mentioned earlier.

Separately, this patch may make non-ASCII input more likely to be classified as a paste block, which can expose an existing code path that does not fully handle non-ASCII input and may panic. Some of this is already being addressed in PR #8647, so I did not submit a separate fix. If this PR is merged, landing PR #8647 first would help.

Aside from that, I am not aware of other panic paths introduced by this patch, though the behavior may still need some observation in practice.

[etraut-openai]

OK, thanks for the update. Very helpful.

It looks like there are some test failures that need attention.

[etraut-openai]

#8774 has been merged, so I'm closing this PR. Thanks again for your work on this @occurrent.