Feature request: Session-boosted ranking in global filter mode

[jul-sh]

Is your feature request related to a problem?

When using filter_mode = "global" with multiple terminal tabs, pressing up-arrow and searching shows commands from all sessions equally. This means commands from other tabs can push this session's recent commands down the list.

The workaround of filter_mode_shell_up_key_binding = "session" limits the up-arrow to only session history, but then searching (typing in the search bar) doesn't show commands from other sessions at all.

Describe the solution

Add a ranking option like session_boost = true or a new filter mode like "session-boosted-global" that:

1. Shows all history (global scope)
2. Ranks current session commands higher in the results

This would let users see their session's history first when pressing up/searching, while still being able to scroll/search into global history when needed.

Alternatives considered

• filter_mode_shell_up_key_binding = "session" — but this hides global history entirely when typing in the search bar
• Manually toggling Ctrl+R to switch filters — adds friction for common workflow
• Native zsh history with INC_APPEND_HISTORY + fzf — loses atuin's benefits (sync, context, stats)