debugger: Fix DebugAdapterDelegate::worktree_root always using the first visible worktree (#32585)

Closes #32577

Release Notes:

- Fixed debugger malfunctioning when using ZED_WORKTREE_ROOT env
variable in multi-worktree workspaces.

crates/debugger_ui/src/debugger_panel.rs

@@ -179,6 +179,19 @@ impl DebugPanel {
                 cx,
             )
         });
+        let worktree = worktree_id.or_else(|| {
+            active_buffer
+                .as_ref()
+                .and_then(|buffer| buffer.read(cx).file())
+                .map(|f| f.worktree_id(cx))
+        });
+        let Some(worktree) = worktree
+            .and_then(|id| self.project.read(cx).worktree_for_id(id, cx))
+            .or_else(|| self.project.read(cx).visible_worktrees(cx).next())
+        else {
+            log::debug!("Could not find a worktree to spawn the debug session in");
+            return;
+        };
         self.debug_scenario_scheduled_last = true;
         if let Some(inventory) = self
             .project
@@ -213,7 +226,7 @@ impl DebugPanel {
                     .await?;
                 dap_store
                     .update(cx, |dap_store, cx| {
-                        dap_store.boot_session(session.clone(), definition, cx)
+                        dap_store.boot_session(session.clone(), definition, worktree, cx)
                     })?
                     .await
             }