refactor: drop dead ExerciseTree.render_manifest

render_manifest had no callers (render_topic is the only one used);
its Manifest/State type imports went with it. Left reset's name-based
snapshot fallback in place — the reset unit tests construct Exercises
with rel_path=None and depend on it.

Author: abhiksark

pythonlings/widgets/exercise_tree.py

@@ -7,32 +7,13 @@
 
 if TYPE_CHECKING:
     from pythonlings.core.exercise import Exercise
-    from pythonlings.core.manifest import Manifest
-    from pythonlings.core.state import State
 
 
 class ExerciseTree(Tree[str]):
     def __init__(self) -> None:
         super().__init__("exercises", id="tree")
         self.show_root = False
 
-    def render_manifest(
-        self, manifest: "Manifest", state: "State", current: str | None
-    ) -> None:
-        self.clear()
-        topics: dict[str, object] = {}
-        for ex in manifest.exercises:
-            if ex.topic not in topics:
-                topics[ex.topic] = self.root.add(ex.topic, expand=True)
-            parent = topics[ex.topic]
-            if ex.name in state.completed:
-                marker = "✓"
-            elif ex.name == current:
-                marker = "●"
-            else:
-                marker = "🔒"
-            parent.add_leaf(f"{marker} {ex.name}", data=ex.name)
-
     def render_topic(
         self,
         topic: str,