feat(profiler/behave_shell): G.8 emotional_valence.frustration_venting

Binary read of ctx.obscenity_hits (G.0 lexical counter):
* detected — obscenity_hits ≥ 1
* none     — zero hits

Skip below FRUST_VENT_MIN_TYPED_CHARS (30). Confidence hard-capped at
0.5: 0.40 when detected, 0.50 only when cleanly absent over ≥ 200
typed letters, 0.30 otherwise.

decnet/profiler/behave_shell/_features/__init__.py

@@ -26,6 +26,7 @@ from decnet.profiler.behave_shell._features.cognitive import (
 )
 from decnet.profiler.behave_shell._features.emotional_valence import (
     arousal,
+    frustration_venting,
     stress_response,
     valence,
 )
@@ -99,4 +100,5 @@ FEATURES: tuple[FeatureFn, ...] = (
     valence,
     arousal,
     stress_response,
+    frustration_venting,
 )