perf(vscode): smoother test explorer refreshes and live test updates

The Test Explorer used to flicker on every keystroke when the tree was
expanded, slow to a crawl during multi-file edits (e.g. when an AI agent
applies many edits at once), and sometimes show "AbortError" as a
workspace entry at startup. Newly added or removed tests didn't appear
in the tree until the refresh button was pressed.

What's different now:

- The tree only re-renders when the discovered tests actually change;
  identical re-discoveries leave the UI untouched.
- One refresh runs at a time — newer edits cancel the in-flight
  subprocess instead of queuing up behind it.
- Many edits in a short window collapse into a single workspace refresh.
- External file changes no longer collapse expanded tree nodes.
- Tests added or removed in a saved file appear/disappear immediately.
- A workspace refresh no longer runs a redundant per-document discover
  for every open file.

Also fixes a non-deterministic tag order from the discover command so
the TS side can reliably detect real tag changes.

Author: d-biehl

packages/runner/src/robotcode/runner/cli/discover/discover.py

@@ -350,7 +350,7 @@ def visit_test(self, test: TestCase) -> None:
                     start=Position(line=test.lineno - 1, character=0),
                     end=Position(line=test.lineno - 1, character=0),
                 ),
-                tags=list(set(normalize(str(t), ignore="_") for t in test.tags)) if test.tags else None,
+                tags=sorted(set(normalize(str(t), ignore="_") for t in test.tags)) if test.tags else None,
                 rpa=self._current.rpa,
             )
         except ValueError as e: