feat: Corpus Intelligence page + timeline background events

Adds /corpus.php — a data transparency page showing what powers the
legal tools: 9 coverage categories with live doc counts, a full
sources table pulled from the corpus DB, the AI stack (LLMs, Whisper,
Qdrant, Azure AI Search, embeddings, chunking), and a pipeline flow
diagram. Stats are live via a new /api/corpus-stats.php endpoint
(queries dobetter_rag + bnl_admin). The reasoning sidebar is repurposed
as a Corpus health panel on this page.

Also ships the in-progress timeline background events toggle:
API and UI wired together via include_background param.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/corpus-stats.php

@@ -0,0 +1,68 @@
+<?php
+declare(strict_types=1);
+
+require_once __DIR__ . '/../includes/bootstrap.php';
+
+dbnToolsRequireMethod('GET');
+dbnToolsRequireAuth();
+
+try {
+    $bnlDb = dbnToolsDb();
+    $ragDb = dbnToolsRagDb();
+
+    // Total documents in the do-better-legal corpus (corpus_id=1)
+    $stmt = $ragDb->prepare('SELECT COUNT(*) FROM documents WHERE corpus_id = 1');
+    $stmt->execute();
+    $totalDocs = (int)$stmt->fetchColumn();
+
+    // Total chunks for corpus_id=1 documents
+    $stmt = $ragDb->prepare(
+        'SELECT COUNT(*) FROM chunks c
+         JOIN documents d ON c.document_id = d.id
+         WHERE d.corpus_id = 1'
+    );
+    $stmt->execute();
+    $totalChunks = (int)$stmt->fetchColumn();
+
+    // Doc counts by category
+    $stmt = $ragDb->prepare(
+        'SELECT category, COUNT(*) AS doc_count
+         FROM documents
+         WHERE corpus_id = 1 AND category IS NOT NULL AND category != \'\'
+         GROUP BY category
+         ORDER BY doc_count DESC'
+    );
+    $stmt->execute();
+    $byCategory = $stmt->fetchAll(PDO::FETCH_ASSOC);
+
+    // Last updated timestamp
+    $stmt = $ragDb->prepare('SELECT MAX(updated_at) FROM documents WHERE corpus_id = 1');
+    $stmt->execute();
+    $lastUpdated = $stmt->fetchColumn() ?: null;
+
+    // Active sources from bnl_admin
+    $stmt = $bnlDb->prepare(
+        'SELECT name, url, category, authority_type, language, schedule, is_active, scraper_class
+         FROM corpus_sources
+         WHERE corpus_id = 1
+         ORDER BY category, name'
+    );
+    $stmt->execute();
+    $sources = $stmt->fetchAll(PDO::FETCH_ASSOC);
+
+    $activeSources = count(array_filter($sources, fn($s) => !empty($s['is_active'])));
+
+    dbnToolsRespond([
+        'ok'    => true,
+        'stats' => [
+            'total_chunks'   => $totalChunks,
+            'total_docs'     => $totalDocs,
+            'active_sources' => $activeSources,
+            'last_updated'   => $lastUpdated,
+            'by_category'    => $byCategory,
+        ],
+        'sources' => $sources,
+    ]);
+} catch (Throwable $e) {
+    dbnToolsError('Could not load corpus statistics: ' . $e->getMessage(), 500, 'corpus_stats_error');
+}

api/timeline.php

@@ -22,7 +22,8 @@ dbnToolsWithTelemetry('timeline', $language, function () use ($input, $language)
     $confidenceFilter = (string)($input['confidence_filter'] ?? '') === 'high_medium'
         ? 'high_medium' : 'all';
 
-    $includeRelative = ($input['include_relative'] ?? true) !== false;
+    $includeRelative   = ($input['include_relative']   ?? true) !== false;
+    $includeBackground = ($input['include_background'] ?? true) !== false;
 
-    return (new DbnLegalToolsService())->timeline($text, $language, $engine, $focus, $confidenceFilter, $includeRelative);
+    return (new DbnLegalToolsService())->timeline($text, $language, $engine, $focus, $confidenceFilter, $includeRelative, $includeBackground);
 });