feat(profiler/behave_shell): emit cognitive.exploration_style

Two-axis classification over the first_token_hash sequence:
repetition_rate (drilling) vs backtrack_rate (jumping among prior
tools). chaotic/targeted/methodical buckets. v0.1 thresholds; D.8
re-tunes.

decnet/profiler/behave_shell/_features/__init__.py

@@ -14,6 +14,7 @@ from decnet.profiler.behave_shell._ctx import SessionContext
 from decnet.profiler.behave_shell._features.cognitive import (
     cognitive_load,
     command_branch_diversity,
+    exploration_style,
     feedback_loop_engagement,
     inter_command_consistency,
     inter_command_latency_class,
@@ -47,4 +48,5 @@ FEATURES: tuple[FeatureFn, ...] = (
     feedback_loop_engagement,
     inter_command_consistency,
     cognitive_load,
+    exploration_style,
 )

decnet/profiler/behave_shell/_features/cognitive.py

@@ -21,6 +21,8 @@ from decnet.profiler.behave_shell._thresholds import (
     COGNITIVE_LOAD_LOW_MAX,
     COGNITIVE_LOAD_MEDIUM_MAX,
     COGNITIVE_LOAD_PACE_REF_CV,
+    EXPLORATION_CHAOTIC_BACKTRACK_MIN,
+    EXPLORATION_TARGETED_REP_MIN,
     FEEDBACK_CORRELATION_MIN,
     FEEDBACK_MIN_PAIRS,
     INTER_CMD_DELIBERATE_MAX,
@@ -179,6 +181,65 @@ def feedback_loop_engagement(ctx: SessionContext) -> Iterator[Observation]:
     )
 
 
+def exploration_style(ctx: SessionContext) -> Iterator[Observation]:
+    """Emit ``cognitive.exploration_style`` ∈ {methodical, chaotic, targeted}.
+
+    Two-axis classification over the first_token_hash sequence:
+
+    * **methodical** — low repetition, low backtracks. Operator marches
+      forward through new tools.
+    * **targeted** — high repetition (R ≥ EXPLORATION_TARGETED_REP_MIN).
+      Same tool re-invoked repeatedly; the operator is drilling.
+    * **chaotic** — high backtrack rate (J ≥ EXPLORATION_CHAOTIC_BACKTRACK_MIN).
+      Jumps among previously-used tools without a clear thread.
+
+    The registry doesn't permit ``unknown``; below the
+    MIN_COMMANDS_FOR_FULL_CONFIDENCE floor we emit at confidence 0.40
+    rather than skip — the engine has *some* signal, just less of it.
+    Skip emission only when there are no commands at all.
+    """
+    n = len(ctx.commands)
+    if n == 0:
+        return
+    hashes = [c.first_token_hash for c in ctx.commands]
+    unique = len(set(hashes))
+    repetition_rate = 0.0 if n == 0 else 1.0 - (unique / n)
+
+    # Backtrack: at position i, hashes[i] previously seen at index < i-1
+    # and not equal to hashes[i-1]. (Repeating the immediate predecessor
+    # is "drilling", picked up by repetition_rate; backtrack is the
+    # non-local jump signal.)
+    seen_before: set[str] = set()
+    backtracks = 0
+    transitions = 0
+    if hashes:
+        seen_before.add(hashes[0])
+    for i in range(1, n):
+        transitions += 1
+        if hashes[i] != hashes[i - 1] and hashes[i] in seen_before:
+            backtracks += 1
+        seen_before.add(hashes[i])
+    backtrack_rate = (backtracks / transitions) if transitions else 0.0
+
+    if backtrack_rate >= EXPLORATION_CHAOTIC_BACKTRACK_MIN:
+        value = "chaotic"
+    elif repetition_rate >= EXPLORATION_TARGETED_REP_MIN:
+        value = "targeted"
+    else:
+        value = "methodical"
+
+    if n < MIN_COMMANDS_FOR_FULL_CONFIDENCE:
+        confidence = 0.40
+    else:
+        confidence = 0.60
+    yield make_observation(
+        ctx,
+        primitive="cognitive.exploration_style",
+        value=value,
+        confidence=confidence,
+    )
+
+
 def cognitive_load(ctx: SessionContext) -> Iterator[Observation]:
     """Emit ``cognitive.cognitive_load`` ∈ {low, medium, high}.
 

decnet/profiler/behave_shell/_thresholds.py

@@ -108,6 +108,26 @@ COGNITIVE_LOAD_PACE_REF_CV: float = 1.50
 COGNITIVE_LOAD_LOW_MAX: float = 0.33
 COGNITIVE_LOAD_MEDIUM_MAX: float = 0.67
 
+# ── cognitive.exploration_style (Step D.2) ─────────────────────────────────
+# Two-axis classification over the first_token_hash sequence:
+#
+#   repetition_rate (R) = 1 - (unique_first_tokens / total_commands)
+#   backtrack_rate  (J) = transitions where commands[i+1].first_token_hash
+#                         appeared anywhere in commands[0..i-1] but is NOT
+#                         equal to commands[i].first_token_hash (jumping
+#                         back to an older tool, not just repeating).
+#
+#   J >= EXPLORATION_CHAOTIC_BACKTRACK_MIN  → chaotic
+#   else if R >= EXPLORATION_TARGETED_REP_MIN → targeted
+#   else                                    → methodical
+#
+# Methodical = low repetition, low backtracks (linear progression through
+# novel tools). Targeted = high repetition (drilling the same tool).
+# Chaotic = jumping between prior tools without a clear thread.
+# v0.1; D.8 re-tunes.
+EXPLORATION_TARGETED_REP_MIN: float = 0.50
+EXPLORATION_CHAOTIC_BACKTRACK_MIN: float = 0.30
+
 # ── 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