Add Summarize Document tool — engine selector, file upload, optional corpus enrichment

- summarize.php: full custom inline form (replaces tool_form.php wrapper) with
  lang switcher, azure_mini/azure_full/gpu engine selector, 8 corpus-slice
  toggles (all off by default), doc picker, file upload zone, and textarea
- api/summarize.php: rewritten to streaming NDJSON (matches barnevernet pattern);
  accepts JSON payload with text, language, engine, slices[], doc_ids[]
- includes/LegalTools.php: adds corpusContextForSummarize() (keyword search via
  ClientRagPipeline) and summarizeWithContext() (engine-aware LLM call with
  optional corpus prepend); returns structured JSON matching existing summarize format
- assets/js/summarize.js: self-contained IIFE handling file upload via
  api/extract.php, slice toggles, NDJSON stream reader, result rendering,
  and trace panel update
- includes/i18n.php: adds 'summarize' to nav in all 4 languages (EN/NO/UK/PL),
  inserted after 'redact' in the tool order with icon 'SZ'

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

api/summarize.php

@@ -2,13 +2,81 @@
 declare(strict_types=1);
 
 require_once __DIR__ . '/../includes/LegalTools.php';
+require_once __DIR__ . '/../includes/ToolModels.php';
 
 dbnToolsRequireMethod('POST');
 dbnToolsRequireAuth();
-$input = dbnToolsJsonInput(70000);
-$language = dbnToolsNormalizeLanguage($input['language'] ?? 'en');
+$ftUid = dbnToolsFreeTierCheck('summarize');
 
-dbnToolsWithTelemetry('summarize', $language, function () use ($input, $language): array {
-    $text = dbnToolsString($input, 'text', 32000);
-    return (new DbnLegalToolsService())->summarize($text, $language);
-});
+$input    = dbnToolsJsonInput(400000);
+$language = dbnToolsNormalizeLanguage($input['language'] ?? 'en');
+$engine   = ToolModels::engineForUser($ftUid, (string)($input['engine'] ?? 'azure_mini'));
+$slices   = is_array($input['slices'] ?? null) ? array_values(array_filter($input['slices'])) : [];
+
+// Streaming headers — flush each NDJSON line as it's written
+header('Content-Type: application/x-ndjson; charset=utf-8');
+header('X-Accel-Buffering: no');
+header('Cache-Control: no-cache, no-store');
+while (ob_get_level()) {
+    ob_end_clean();
+}
+
+$emit = static function (string $event, array $payload): void {
+    echo json_encode(['event' => $event] + $payload, JSON_UNESCAPED_UNICODE) . "\n";
+    flush();
+};
+
+try {
+    $text = dbnToolsInjectDocContent($input, dbnToolsString($input, 'text', 128000));
+
+    if (mb_strlen(trim($text), 'UTF-8') < 50) {
+        $emit('error', [
+            'error' => 'Paste text, upload a file, or select a document before running.',
+            'code'  => 'empty_text',
+        ]);
+        exit;
+    }
+
+    $emit('progress', [
+        'step'   => 'text_ready',
+        'detail' => mb_strlen($text, 'UTF-8') . ' chars ready.',
+    ]);
+
+    $corpusContext = '';
+    if (!empty($slices)) {
+        $sliceCount = count($slices);
+        $emit('progress', [
+            'step'   => 'corpus_search',
+            'detail' => 'Searching legal corpus (' . $sliceCount . ' slice' . ($sliceCount === 1 ? '' : 's') . ')…',
+        ]);
+        $svc           = new DbnLegalToolsService();
+        $query         = mb_substr(trim($text), 0, 600, 'UTF-8');
+        $corpusContext = $svc->corpusContextForSummarize($query, 8);
+        $emit('progress', [
+            'step'   => 'corpus_done',
+            'detail' => $corpusContext !== ''
+                ? 'Legal context retrieved.'
+                : 'No matching passages found; summarising without corpus.',
+        ]);
+    }
+
+    $emit('progress', [
+        'step'   => 'generating',
+        'detail' => 'Generating summary…',
+    ]);
+
+    $result = (new DbnLegalToolsService())->summarizeWithContext($text, $language, $engine, $corpusContext);
+
+    if ($ftUid > 0) {
+        $balance          = dbnToolsFreeTierDeduct($ftUid, 'summarize');
+        $result['balance'] = $balance;
+    }
+
+    $emit('final', $result);
+
+} catch (DbnToolsHttpException $e) {
+    $emit('error', ['error' => $e->getMessage(), 'code' => (string)$e->getCode()]);
+} catch (Throwable $e) {
+    error_log('summarize error: ' . $e->getMessage());
+    $emit('error', ['error' => 'An unexpected error occurred. Please try again.', 'code' => 'server_error']);
+}