feat(profiler/behave_shell): emit cognitive.tool_vocabulary

Absolute distinct first_token_hash count, bucketed against
TOOL_VOCAB_NARROW_MAX / TOOL_VOCAB_BROAD_MIN. v0.1; D.8 re-tunes.

decnet/profiler/behave_shell/_features/__init__.py

@@ -17,6 +17,7 @@ from decnet.profiler.behave_shell._features.cognitive import (
     exploration_style,
     feedback_loop_engagement,
     planning_depth,
+    tool_vocabulary,
     inter_command_consistency,
     inter_command_latency_class,
 )
@@ -51,4 +52,5 @@ FEATURES: tuple[FeatureFn, ...] = (
     cognitive_load,
     exploration_style,
     planning_depth,
+    tool_vocabulary,
 )

decnet/profiler/behave_shell/_features/cognitive.py

@@ -36,6 +36,8 @@ from decnet.profiler.behave_shell._thresholds import (
     PAUSE_CV_METRONOMIC_MAX,
     PLANNING_DEEP_MIN,
     PLANNING_REACTIVE_MIN,
+    TOOL_VOCAB_BROAD_MIN,
+    TOOL_VOCAB_NARROW_MAX,
 )
 
 
@@ -184,6 +186,35 @@ def feedback_loop_engagement(ctx: SessionContext) -> Iterator[Observation]:
     )
 
 
+def tool_vocabulary(ctx: SessionContext) -> Iterator[Observation]:
+    """Emit ``cognitive.tool_vocabulary`` ∈ {narrow, moderate, broad}.
+
+    Absolute count of distinct first_token_hashes. Skip emission when
+    no commands exist; below the sample-size floor we still emit, but
+    at confidence 0.40 — a session with few commands but five distinct
+    tools is genuinely a moderate-vocabulary signal.
+    """
+    if not ctx.commands:
+        return
+    distinct = len({c.first_token_hash for c in ctx.commands})
+    if distinct <= TOOL_VOCAB_NARROW_MAX:
+        value = "narrow"
+    elif distinct >= TOOL_VOCAB_BROAD_MIN:
+        value = "broad"
+    else:
+        value = "moderate"
+    if len(ctx.commands) < MIN_COMMANDS_FOR_FULL_CONFIDENCE:
+        confidence = 0.40
+    else:
+        confidence = 0.70
+    yield make_observation(
+        ctx,
+        primitive="cognitive.tool_vocabulary",
+        value=value,
+        confidence=confidence,
+    )
+
+
 def planning_depth(ctx: SessionContext) -> Iterator[Observation]:
     """Emit ``cognitive.planning_depth`` ∈ {deep, shallow, reactive}.
 

decnet/profiler/behave_shell/_thresholds.py

@@ -141,6 +141,20 @@ EXPLORATION_CHAOTIC_BACKTRACK_MIN: float = 0.30
 PLANNING_DEEP_MIN: float = 0.40
 PLANNING_REACTIVE_MIN: float = 0.50
 
+# ── cognitive.tool_vocabulary (Step D.4) ───────────────────────────────────
+# Absolute count of distinct first_token_hashes across the session.
+#
+#   distinct <= TOOL_VOCAB_NARROW_MAX  → narrow
+#   distinct >= TOOL_VOCAB_BROAD_MIN   → broad
+#   otherwise                          → moderate
+#
+# Absolute, not normalised. A 3-command session with 3 unique tools is
+# ``narrow`` not ``broad`` — the operator simply hasn't shown range yet.
+# Sample-size honesty drops confidence below MIN_COMMANDS_FOR_FULL_CONFIDENCE.
+# v0.1; D.8 re-tunes.
+TOOL_VOCAB_NARROW_MAX: int = 3
+TOOL_VOCAB_BROAD_MIN: int = 10
+
 # ── motor.keystroke_cadence (Step B.1) ──────────────────────────────────────
 # Typing bursts split at gaps > IKI_THINK_MAX_S so think-pauses between
 # commands don't inflate the within-burst CV. Mirrors the prototype's