feat(graceful-handoff): 2.0 — statusLine context-percent hint [skip-docs]

Step 4 of v2.0 plan. statusLine hook reads context_window.used_percentage
from stdin payload and prints display-only hint at 60% / 70%. NEVER runs
git (research/03 — statusLine scripts can be cancelled mid-flight, unsafe
for side effects). 9 tests cover thresholds, null payload, malformed JSON.
Includes hook-helper.mjs copied from llm-security as test infrastructure.

plugins/graceful-handoff/tests/hooks/statusline-monitor.test.mjs

@@ -0,0 +1,78 @@
+// statusline-monitor.test.mjs — Tests statusLine hook display thresholds.
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { runHook } from './hook-helper.mjs';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const HOOK = join(__dirname, '..', '..', 'hooks', 'scripts', 'statusline-monitor.mjs');
+
+function payload(usedPercentage) {
+  return {
+    context_window: {
+      used_percentage: usedPercentage,
+      remaining_percentage: usedPercentage == null ? null : 100 - usedPercentage,
+      context_window_size: 200000,
+    },
+    model: { id: 'claude-opus-4-7', display_name: 'Opus' },
+    session_id: 'test-session',
+  };
+}
+
+test('< 60%: silent, no output', async () => {
+  const res = await runHook(HOOK, payload(45));
+  assert.equal(res.code, 0);
+  assert.equal(res.stdout.trim(), '', `expected empty stdout, got: "${res.stdout}"`);
+});
+
+test('60-69%: prints "vurder /graceful-handoff" hint with "60" or "kontekst" substring', async () => {
+  const res = await runHook(HOOK, payload(63));
+  assert.equal(res.code, 0);
+  assert.match(res.stdout, /kontekst/);
+  assert.match(res.stdout, /vurder.*graceful-handoff/);
+});
+
+test('≥ 70%: prints stronger hint with "kjør NÅ"', async () => {
+  const res = await runHook(HOOK, payload(75));
+  assert.equal(res.code, 0);
+  assert.match(res.stdout, /kontekst/);
+  assert.match(res.stdout, /kjør.*graceful-handoff.*NÅ/i);
+});
+
+test('exact threshold 60%: shows hint (not silent)', async () => {
+  const res = await runHook(HOOK, payload(60));
+  assert.equal(res.code, 0);
+  assert.match(res.stdout, /60/);
+});
+
+test('exact threshold 70%: shows urgent hint', async () => {
+  const res = await runHook(HOOK, payload(70));
+  assert.equal(res.code, 0);
+  assert.match(res.stdout, /NÅ/);
+});
+
+test('null used_percentage: silent (early session before first API call)', async () => {
+  const res = await runHook(HOOK, payload(null));
+  assert.equal(res.code, 0);
+  assert.equal(res.stdout.trim(), '');
+});
+
+test('missing context_window field: silent', async () => {
+  const res = await runHook(HOOK, { model: { id: 'foo' }, session_id: 'x' });
+  assert.equal(res.code, 0);
+  assert.equal(res.stdout.trim(), '');
+});
+
+test('empty stdin: silent', async () => {
+  const res = await runHook(HOOK, '');
+  assert.equal(res.code, 0);
+  assert.equal(res.stdout.trim(), '');
+});
+
+test('malformed JSON: silent (no crash)', async () => {
+  const res = await runHook(HOOK, '{not json');
+  assert.equal(res.code, 0);
+  assert.equal(res.stdout.trim(), '');
+});