Introduce performable: prefix for keybind triggers to passthrough if they would do nothing

[mitchellh]

Discussion: #2811

The discussion was focused on copy but this could apply to many different actions so I think we should generalize it. Ghostty already has a mechanism in performBindingAction to determine if a binding action was performed or not. We can use that.

The new prefix performable: (similar to other prefixes like unconsumed:, all:, global:) would be a new modifier with the following effect:

Details

performable:-prefixed triggers will only apply at all if they can be performed. If they can't be performed, they act as if the keybinding doesn't exist. For example, this can be used with copy to copy or send an interrupt signal:

keybind = performable:ctrl+c=copy_to_clipboard

This trigger interacts with the other prefixes in the following way:

• global: - No effect. Global actions are always considered performed.
• all: - No effect. All actions are always considered performed.
• unconsumed: - Only applies if the action is performable. These two sort of cancel each other out so it's odd to use them both, but it doesn't cause problems.

[rinormaloku]

This is not working as intended, on the latest commit, when there is nothing to copy it is not passing through to termination.

Screenshare.-.2025-01-07.3_16_55.PM.mp4

[mitchellh]

This is not working as intended, on the latest commit, when there is nothing to copy it is not passing through to termination.

#4522 is the problem. Fixed for macOS, unsure yet how to fix for GTK.