feat: keep picker context for auxiliary actions

[barrettruth]

Summary

• keep non-consuming picker actions like web open, copy, and PR worktree open across all picker backends
• reopen or refresh the relevant picker after mutating actions so list workflows stay in context instead of dead-ending
• add backend and picker specs covering close-vs-stay behavior for fzf-lua, Telescope, and Snacks

Test plan

• bash scripts/ci.sh
• busted spec/fzf_picker_spec.lua spec/telescope_picker_spec.lua spec/snacks_picker_spec.lua spec/pickers_spec.lua