Add full-text search index over guides, steps, blocks, and placeholders

Pure-JS inverted index persisted under library/index/ (documented FTS5
fallback). AND queries, last-token prefix matching, title boosting,
step deep-links, snippets. 4 workflow tests (23 total).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/unit/search.test.js

@@ -0,0 +1,110 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const path = require('node:path');
+
+const { GuideStore } = require('../../core/store');
+const { SearchIndex } = require('../../core/search');
+const { makeTmpDir, rmrf, TINY_PNG } = require('./helpers');
+
+function buildLibrary(root) {
+  const store = new GuideStore(root);
+  const index = new SearchIndex(store.indexDir);
+
+  const vpn = store.createGuide({
+    title: 'Install the VPN client',
+    descriptionHtml: '<p>Corporate network access</p>',
+    placeholders: { Department: 'Infrastructure' },
+  });
+  store.addStep(vpn.guideId, { title: 'Download installer from portal' }, TINY_PNG, { width: 1, height: 1 });
+  store.addStep(vpn.guideId, {
+    kind: 'content',
+    title: 'Configure split tunneling',
+    descriptionHtml: '<p>Set the <b>gateway</b> to vpn.example.com</p>',
+    codeBlocks: [{ id: 'cb1', language: 'bash', code: 'sudo systemctl restart openvpn' }],
+  });
+
+  const pw = store.createGuide({ title: 'Reset user password' });
+  store.addStep(pw.guideId, {
+    title: 'Open admin console',
+    textBlocks: [{ title: 'Permissions', descriptionHtml: '<p>Requires the helpdesk role</p>', level: 'warn' }],
+  });
+
+  index.indexGuide(store.getGuide(vpn.guideId), store.listSteps(vpn.guideId));
+  index.indexGuide(store.getGuide(pw.guideId), store.listSteps(pw.guideId));
+  return { store, index, vpn, pw };
+}
+
+test('full-text search finds guides and deep-links steps by body content', (t) => {
+  const root = makeTmpDir('search');
+  t.after(() => rmrf(root));
+  const { index, vpn, pw } = buildLibrary(root);
+
+  // Body text inside a code block is searchable and points at the step.
+  const codeHits = index.search('openvpn');
+  assert.equal(codeHits.length, 1);
+  assert.equal(codeHits[0].guideId, vpn.guideId);
+  assert.ok(codeHits[0].stepId, 'code block hit should deep-link to its step');
+  assert.ok(codeHits[0].snippet.includes('systemctl restart openvpn'));
+
+  // Text block content is searchable too.
+  const tbHits = index.search('helpdesk');
+  assert.equal(tbHits.length, 1);
+  assert.equal(tbHits[0].guideId, pw.guideId);
+
+  // Placeholder values are indexed at guide level.
+  const phHits = index.search('Infrastructure');
+  assert.ok(phHits.some((h) => h.guideId === vpn.guideId && h.stepId === null));
+});
+
+test('multi-token AND queries and prefix matching on the last token', (t) => {
+  const root = makeTmpDir('search2');
+  t.after(() => rmrf(root));
+  const { index, vpn } = buildLibrary(root);
+
+  // Both tokens must match the same document.
+  assert.equal(index.search('split tunneling').length, 1);
+  assert.equal(index.search('split helpdesk').length, 0);
+
+  // Search-as-you-type: trailing token matches as a prefix.
+  const typed = index.search('tunn');
+  assert.equal(typed.length, 1);
+  assert.equal(typed[0].guideId, vpn.guideId);
+
+  // Title hits outrank body hits.
+  const ranked = index.search('vpn');
+  assert.equal(ranked[0].title, 'Install the VPN client');
+});
+
+test('index survives reload from disk and removal works', (t) => {
+  const root = makeTmpDir('search3');
+  t.after(() => rmrf(root));
+  const { store, vpn, pw } = buildLibrary(root);
+
+  const reloaded = new SearchIndex(store.indexDir);
+  assert.ok(reloaded.search('password').some((h) => h.guideId === pw.guideId));
+
+  reloaded.removeGuide(vpn.guideId);
+  assert.equal(reloaded.search('tunneling').length, 0);
+  // Removal persisted: a fresh instance agrees.
+  assert.equal(new SearchIndex(store.indexDir).search('tunneling').length, 0);
+});
+
+test('re-indexing a changed guide replaces stale content', (t) => {
+  const root = makeTmpDir('search4');
+  t.after(() => rmrf(root));
+  const { store, index, vpn } = buildLibrary(root);
+
+  const guide = store.getGuide(vpn.guideId);
+  guide.title = 'Install the ZeroTrust agent';
+  store.saveGuide(guide);
+  index.indexGuide(store.getGuide(vpn.guideId), store.listSteps(vpn.guideId));
+
+  assert.equal(index.searchTitles('vpn').length, 0, 'old title must be gone');
+  assert.equal(index.searchTitles('zerotrust').length, 1);
+
+  // titles-only search excludes step-level matches.
+  assert.equal(index.searchTitles('gateway').length, 0);
+  assert.ok(index.search('gateway').length >= 1);
+});