refactor(pi052): trim PR — remove say tool, debug gates, dead code; move runtime

Cleanup pass over the language-support PR to cut LOC and scope creep.

Removals:
- SayTool + tools/ package (registry, Tool protocol, [tools] extra) and the
  runtime's tool-dispatch path. Kept <say> training supervision and inference
  stripping so speech-annotated datasets still train.
- WeightedEpisodeAwareSampler + VQA oversampling wiring
  (_build_vqa_oversample_weights, vqa_target_fraction) — training uses plain
  EpisodeAwareSampler again.
- Debug env-gates PI052_DEBUG_TENSORS, PI052_SUBTASK_USE_TASK, EVAL_TASK_OVERRIDE.
- Dead code: broken _tp._DUMP_BUDGET block, unused imports (copy/Tensor,
  RevisionNotFoundError, LeRobotDataset, os), messages_for_vqa, steps.py shim
  (modeling imports pi052_adapter directly), duplicated _emit, builtins.type[T].

Moves:
- Policy-agnostic runtime -> src/lerobot/runtime/ (LanguageConditionedRuntime +
  adapter Protocol + state); pi052 keeps only its adapter + CLI. Tests -> tests/runtime/.

Other:
- Compacted verbose AI-authored comments/docstrings across pi052 (kept the
  hard-won DDP / barrier-timeout / reduce-max / VQA-routing notes).
- Relocated LM-head prediction debug helper to pi052/debug_utils.py.
- Fixed test_render_messages: assert task-fallback render (current behavior)
  instead of the stale no-op expectation.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/processor/test_render_messages_processor.py

@@ -12,7 +12,9 @@ from lerobot.processor.render_messages_processor import RenderMessagesStep  # no
 from lerobot.types import TransitionKey  # noqa: E402
 
 
-def test_render_messages_step_noops_without_language_columns():
+def test_render_messages_step_renders_task_fallback_without_language_columns():
+    """No language columns + a task string → low-level task fallback render,
+    matching what the policy sees at eval time on unannotated observations."""
     recipe = TrainingRecipe(
         messages=[
             MessageTurn(role="user", content="${task}", stream="high_level"),
@@ -21,6 +23,24 @@ def test_render_messages_step_noops_without_language_columns():
     )
     transition = create_transition(complementary_data={"task": "do it"})
 
+    out = RenderMessagesStep(recipe)(transition)
+    data = out[TransitionKey.COMPLEMENTARY_DATA]
+
+    assert data["messages"] == [{"role": "user", "content": "do it"}]
+    assert data["message_streams"] == ["low_level"]
+    assert data["target_message_indices"] == []
+    assert data["task"] == "do it"
+
+
+def test_render_messages_step_noops_without_language_columns_or_task():
+    recipe = TrainingRecipe(
+        messages=[
+            MessageTurn(role="user", content="${task}", stream="high_level"),
+            MessageTurn(role="assistant", content="${subtask}", stream="low_level", target=True),
+        ]
+    )
+    transition = create_transition(complementary_data={})
+
     assert RenderMessagesStep(recipe)(transition) == transition