test(decnet_web): vitest coverage for Behavioural primitives panel

Four tests pin the panel surface:
* Empty-state placeholder renders when no observations.
* Day-one priority primitives sort to the top of their group:
  motor.input_modality first in motor; the three cognitive priority
  primitives in documented order at the top of cognitive.
* Each row renders primitive leaf, value, and confidence-percent
  badge.
* Groups follow the canonical domain order
  (motor / cognitive / temporal / operational / environmental /
  emotional_valence); unknown domains alphabetise at the end.

Mirrors the Orchestrator.test.tsx harness shape (DEBT-043). Live
update path (useAttackerStream → setObservations) is exercised
indirectly via the static render — the hook is dumb glue and the
state mutation is React-side.

decnet_web/src/components/AttackerDetail.behaviour_panel.test.tsx

@@ -0,0 +1,87 @@
+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+
+import {
+  BehaviouralPrimitivesPanel,
+  type BehaviouralObservation,
+} from './AttackerDetail';
+
+const _obs = (
+  primitive: string,
+  value: unknown,
+  confidence = 0.85,
+): BehaviouralObservation => ({
+  primitive,
+  value,
+  confidence,
+  ts: 1714521660.456,
+  source: 'test',
+});
+
+describe('BehaviouralPrimitivesPanel', () => {
+  it('renders an empty-state placeholder when no observations', () => {
+    render(<BehaviouralPrimitivesPanel observations={[]} />);
+    expect(screen.getByTestId('behaviour-empty')).toBeInTheDocument();
+  });
+
+  it('places day-one priority primitives at the top of their group', () => {
+    // Mix priority + non-priority primitives in arbitrary input order.
+    const observations: BehaviouralObservation[] = [
+      _obs('motor.keystroke_cadence', 'steady'),
+      _obs('cognitive.tool_vocabulary', 'broad'),
+      _obs('motor.input_modality', 'typed'), // priority #1
+      _obs('cognitive.feedback_loop_engagement', 'closed_loop'), // priority #2
+      _obs('cognitive.command_branch_diversity', 'adaptive_branching'), // #3
+      _obs('cognitive.inter_command_latency_class', 'typing_speed'), // #4
+      _obs('motor.error_correction', 'immediate'),
+    ];
+    render(<BehaviouralPrimitivesPanel observations={observations} />);
+
+    // motor group: input_modality must precede the alphabetised rest.
+    const motorRows = Array.from(
+      document.querySelectorAll('[data-testid^="behaviour-row-motor."]'),
+    ).map((el) => el.getAttribute('data-testid')!);
+    expect(motorRows[0]).toBe('behaviour-row-motor.input_modality');
+
+    // cognitive group: the three priority primitives must be in the
+    // documented order at the top.
+    const cogRows = Array.from(
+      document.querySelectorAll('[data-testid^="behaviour-row-cognitive."]'),
+    ).map((el) => el.getAttribute('data-testid')!);
+    expect(cogRows.slice(0, 3)).toEqual([
+      'behaviour-row-cognitive.feedback_loop_engagement',
+      'behaviour-row-cognitive.command_branch_diversity',
+      'behaviour-row-cognitive.inter_command_latency_class',
+    ]);
+  });
+
+  it('renders the primitive value and a confidence badge', () => {
+    const observations: BehaviouralObservation[] = [
+      _obs('motor.input_modality', 'pasted', 0.91),
+    ];
+    render(<BehaviouralPrimitivesPanel observations={observations} />);
+    const row = screen.getByTestId('behaviour-row-motor.input_modality');
+    expect(row.textContent).toContain('input_modality');
+    expect(row.textContent).toContain('pasted');
+    expect(row.textContent).toContain('91%');
+  });
+
+  it('groups by top-level domain in the canonical order', () => {
+    const observations: BehaviouralObservation[] = [
+      _obs('emotional_valence.arousal', 'medium_engaged'),
+      _obs('temporal.session_duration', 'medium'),
+      _obs('motor.input_modality', 'typed'),
+      _obs('cognitive.cognitive_load', 'medium'),
+    ];
+    render(<BehaviouralPrimitivesPanel observations={observations} />);
+    const groups = Array.from(
+      document.querySelectorAll('[data-testid^="behaviour-group-"]'),
+    ).map((el) => el.getAttribute('data-testid')!);
+    expect(groups).toEqual([
+      'behaviour-group-motor',
+      'behaviour-group-cognitive',
+      'behaviour-group-temporal',
+      'behaviour-group-emotional_valence',
+    ]);
+  });
+});