feat(profiler/behave_shell): emit temporal.session_duration

Bucket ctx.duration_s against SESSION_DURATION_SHORT_MAX (60s) /
MEDIUM_MAX (600s) / LONG_MAX (3600s); else marathon. Direct
measurement, confidence 0.85. Skip emission only when no commands
and zero duration. New _features/temporal.py module opens Phase E.

decnet/profiler/behave_shell/_features/__init__.py

@@ -24,6 +24,9 @@ from decnet.profiler.behave_shell._features.cognitive import (
     inter_command_consistency,
     inter_command_latency_class,
 )
+from decnet.profiler.behave_shell._features.temporal import (
+    session_duration,
+)
 from decnet.profiler.behave_shell._features.motor import (
     command_chunking,
     error_correction,
@@ -59,4 +62,5 @@ FEATURES: tuple[FeatureFn, ...] = (
     error_resilience_retry_tactic,
     error_resilience_frustration_typing,
     error_resilience_fallback_to_man,
+    session_duration,
 )

decnet/profiler/behave_shell/_features/temporal.py

@@ -0,0 +1,50 @@
+"""``temporal.*`` feature functions — per-session subset.
+
+Phase E ships the four ``temporal.*`` primitives that don't need
+observation history. The other three (``session_timing``,
+``persistence``, ``lifecycle_markers.idle_periodicity``) are Tier B
+and computed by the attribution engine, not the extractor.
+
+Step E.1: ``temporal.session_duration``.
+"""
+from __future__ import annotations
+
+from typing import Iterator
+
+from decnet_behave_core.spec.envelope import Observation
+
+from decnet.profiler.behave_shell._ctx import SessionContext
+from decnet.profiler.behave_shell._features._emit import make_observation
+from decnet.profiler.behave_shell._thresholds import (
+    SESSION_DURATION_LONG_MAX,
+    SESSION_DURATION_MEDIUM_MAX,
+    SESSION_DURATION_SHORT_MAX,
+)
+
+
+def session_duration(ctx: SessionContext) -> Iterator[Observation]:
+    """Emit ``temporal.session_duration`` ∈ {short, medium, long, marathon}.
+
+    Direct measurement off ``ctx.duration_s``. Skip emission only when
+    the session has neither commands nor any duration to speak of —
+    a one-event session with ``duration_s == 0`` and no commands has
+    nothing honest to bucket. Confidence is high — duration is a fact,
+    not an inference.
+    """
+    if ctx.duration_s <= 0.0 and not ctx.commands:
+        return
+    d = ctx.duration_s
+    if d < SESSION_DURATION_SHORT_MAX:
+        value = "short"
+    elif d < SESSION_DURATION_MEDIUM_MAX:
+        value = "medium"
+    elif d < SESSION_DURATION_LONG_MAX:
+        value = "long"
+    else:
+        value = "marathon"
+    yield make_observation(
+        ctx,
+        primitive="temporal.session_duration",
+        value=value,
+        confidence=0.85,
+    )