annotate: make full-episode subtask coverage unconditional

Remove the subtask_full_coverage config flag. Stitching subtask spans
into a contiguous full-episode cover is now always applied in
_generate_subtasks — a sparse / gap-ridden subtask timeline is never
desirable for conditioning, so there's no reason to make it optional.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lerobot/annotations/steerable_pipeline/config.py

@@ -73,15 +73,12 @@ class PlanConfig:
     # nothing). +1 VLM call/ep.
     subtask_verify: bool = True
 
-    # ``subtask_full_coverage``: deterministic post-step (no VLM call)
-    # that stitches the surviving subtask spans into a contiguous cover
-    # of the whole episode — first subtask pulled back to t0, each span's
-    # end snapped to the next span's start, last span extended to t_last.
-    # Without it the verify pass (which prunes spans) can leave the
-    # subtask timeline starting late or full of gaps, so frames fall
-    # through with no active subtask. On by default; disable only if a
-    # downstream consumer genuinely wants sparse (non-tiling) subtasks.
-    subtask_full_coverage: bool = True
+    # NOTE: subtask spans are ALWAYS stitched into a contiguous
+    # full-episode cover (first subtask pulled back to t0, gaps closed,
+    # last span extended to t_last) as a deterministic post-step in
+    # ``_generate_subtasks._stitch_full_coverage``. This is not
+    # configurable — a sparse / gap-ridden subtask timeline is never
+    # desirable for conditioning, so it is unconditional.
 
     # When True (and backend supports it, e.g. ``openai``), the ``plan``
     # module sends a ``video_url`` block pointing at a per-episode mp4

src/lerobot/annotations/steerable_pipeline/modules/plan_subtasks_memory.py

@@ -578,10 +578,11 @@ class PlanSubtasksMemoryModule:
         # The VLM (especially after the verify pass prunes spans) can
         # leave the first subtask starting after t0 or leave gaps between
         # spans, so the subtask timeline no longer tiles the whole
-        # episode and frames fall through with no active subtask. Stitch
-        # the surviving spans into a contiguous cover of [t0, t_last].
-        if getattr(self.config, "subtask_full_coverage", True):
-            cleaned = self._stitch_full_coverage(cleaned, record)
+        # episode and frames fall through with no active subtask. Always
+        # stitch the surviving spans into a contiguous cover of
+        # [t0, t_last] — there is no scenario where a sparse, gap-ridden
+        # subtask timeline is desirable for conditioning.
+        cleaned = self._stitch_full_coverage(cleaned, record)
 
         return cleaned