fix(cmd): restore param mode for connector commands, route item selection through execute
The previous fix disabled param mode entirely for connector commands (those
with produces), which broke autocomplete for the edit command. This restores
param mode so autocomplete works, and fixes acceptParamSuggestion() to route
item-type param selections through execute() instead of directly publishing
editor:open. This way the command's output handling flow works correctly
(enters output selection mode for multiple results, routes to editor for
single items, supports chaining).
Also adds a Playwright test for the edit+Tab flow verifying that param mode
activates, suggestions appear, and selecting one triggers editor:open.