Improve /tabs completion workflow (#16168)

Follow-up of https://github.com/zed-industries/zed/pull/16154

Reworks /tabs arguments to allow:
* current tab by default, if no arguments are present
* fuzzy-matching over paths of the related tabs
* `all` case to insert all tabs at once

Release Notes:

- N/A

crates/assistant/src/slash_command/terminal_command.rs

@@ -45,7 +45,7 @@ impl SlashCommand for TerminalSlashCommand {
         _query: String,
         _cancel: Arc<AtomicBool>,
         _workspace: Option<WeakView<Workspace>>,
-        _cx: &mut AppContext,
+        _cx: &mut WindowContext,
     ) -> Task<Result<Vec<ArgumentCompletion>>> {
         Task::ready(Ok(vec![ArgumentCompletion {
             label: LINE_COUNT_ARG.to_string(),