feat: add ECC statusline observability hooks

Salvages the useful statusline/context monitor work from stale PR #1504 while preserving the current continuous-learning hook runner wiring.

Adds the metrics bridge, context monitor, statusline script, shared cost/session bridge utilities, and tests. Fixes the reviewed false loop-detection hash collision for non-file tools, avoids default-session cost inflation, sanitizes statusline task lookup, and records hook payload session IDs in cost-tracker.

tests/lib/cost-estimate.test.js

@@ -0,0 +1,114 @@
+/**
+ * Tests for scripts/lib/cost-estimate.js
+ *
+ * Run with: node tests/lib/cost-estimate.test.js
+ */
+
+const assert = require('assert');
+
+const { estimateCost, RATE_TABLE } = require('../../scripts/lib/cost-estimate');
+
+// Test helper
+function test(name, fn) {
+  try {
+    fn();
+    console.log(`  \u2713 ${name}`);
+    return true;
+  } catch (err) {
+    console.log(`  \u2717 ${name}`);
+    console.log(`    Error: ${err.message}`);
+    return false;
+  }
+}
+
+function runTests() {
+  console.log('\n=== Testing cost-estimate.js ===\n');
+
+  let passed = 0;
+  let failed = 0;
+
+  // RATE_TABLE structure
+  console.log('RATE_TABLE:');
+
+  if (
+    test('RATE_TABLE has haiku, sonnet, opus keys', () => {
+      assert.ok(RATE_TABLE.haiku, 'Missing haiku');
+      assert.ok(RATE_TABLE.sonnet, 'Missing sonnet');
+      assert.ok(RATE_TABLE.opus, 'Missing opus');
+      assert.strictEqual(typeof RATE_TABLE.haiku.in, 'number');
+      assert.strictEqual(typeof RATE_TABLE.haiku.out, 'number');
+      assert.strictEqual(typeof RATE_TABLE.sonnet.in, 'number');
+      assert.strictEqual(typeof RATE_TABLE.sonnet.out, 'number');
+      assert.strictEqual(typeof RATE_TABLE.opus.in, 'number');
+      assert.strictEqual(typeof RATE_TABLE.opus.out, 'number');
+    })
+  )
+    passed++;
+  else failed++;
+
+  // estimateCost tests
+  console.log('\nestimateCost:');
+
+  if (
+    test('opus 1M/1M tokens returns 90', () => {
+      const cost = estimateCost('opus', 1_000_000, 1_000_000);
+      assert.strictEqual(cost, 90);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('sonnet 1M/1M tokens returns 18', () => {
+      const cost = estimateCost('sonnet', 1_000_000, 1_000_000);
+      assert.strictEqual(cost, 18);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('haiku 1M/1M tokens returns 4.8', () => {
+      const cost = estimateCost('haiku', 1_000_000, 1_000_000);
+      assert.strictEqual(cost, 4.8);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('null model with 0 tokens returns 0', () => {
+      const cost = estimateCost(null, 0, 0);
+      assert.strictEqual(cost, 0);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('full model name claude-opus-4-6 uses opus rates', () => {
+      const cost = estimateCost('claude-opus-4-6', 500, 200);
+      // (500 / 1_000_000) * 15 + (200 / 1_000_000) * 75 = 0.0075 + 0.015 = 0.0225
+      const expected = Math.round(0.0225 * 1e6) / 1e6;
+      assert.strictEqual(cost, expected);
+    })
+  )
+    passed++;
+  else failed++;
+
+  if (
+    test('unknown model falls back to sonnet rates', () => {
+      const cost = estimateCost('unknown-model', 1_000_000, 1_000_000);
+      assert.strictEqual(cost, 18);
+    })
+  )
+    passed++;
+  else failed++;
+
+  // Summary
+  console.log(`\nResults: ${passed} passed, ${failed} failed\n`);
+  return { passed, failed };
+}
+
+const { failed } = runTests();
+process.exit(failed > 0 ? 1 : 0);