[Feature Request] Add configurable auto-compaction threshold setting

Bug Description
Feature request: configurable auto-compaction threshold

Auto-compaction is currently on/off only, with the trigger hard-coded near the context limit. I'd like an opt-in threshold, e.g. compact at 60-70% instead of waiting until nearly full.

I get that the default is right for most users and that compaction is lossy. But for power users managing their own context, an optional setting (autoCompactThreshold, 0.0-1.0) would be genuinely useful. Manual /compact works but relies on me catching the right moment instead of the tool handling it at a point I've chosen.

Keep the default unchanged, just expose the knob for those who want it. On a 1M window the gap is especially noticeable.

Thanks!

Environment Info

• Platform: darwin
• Terminal: tmux
• Version: 2.1.168
• Feedback ID: baa077c8-13e3-42fb-9f6f-6f894f7e62dd

Errors

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