fix(tools): parse-harden Do Better Legal ask against leaky fine-tune output

The dbn-legal-agent-v3 fine-tune (Track 1 / family) emits a labelled-prose
template — duplicate `answer:` prefixes, markdown-escaped underscores (`\_`),
and a trailing raw JSON blob — rather than the strict JSON the Azure/gpt-4o
path produces via response_format. decodeJsonObject() returned null on that
invalid JSON, so ask() dumped the entire raw blob into `answer`.

Fix at the parse layer (no upstream response_format change, to avoid fighting
the fine-tune's training):
- dbnToolsRepairJsonText(): strip fences, drop only invalid `\_`/`\*` escapes,
  then balanced-brace scan collecting every top-level {...} (longest first) to
  recover an appended JSON object. Shared by both gateways' decodeJsonObject(),
  so all JSON tools benefit.
- dbnToolsParseLabeledFields(): parse labelled-prose into real fields when no
  JSON decodes, tolerating escaped key names and collapsing duplicate prefixes.
- ask() null-fallback now builds clean structured fields from the parsed prose
  instead of dumping raw; what_remains_uncertain becomes a proper list.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

includes/bootstrap.php

@@ -1461,6 +1461,117 @@ function dbnToolsExtractCleanAnswer(string $text): string
     return trim($text);
 }
 
+/**
+ * Robustly extract a JSON object from a model reply, tolerating the artifacts the
+ * fine-tuned models leak: ```fences```, markdown-escaped underscores/asterisks
+ * (`\_`, `\*` — never valid JSON escapes), and prose wrapped around a real JSON
+ * blob. Returns the decoded array, or null if nothing parses. Shared by both
+ * gateways' decodeJsonObject(), so every JSON tool benefits.
+ */
+function dbnToolsRepairJsonText(string $content): ?array
+{
+    $content = trim($content);
+    $content = (string)preg_replace('/^```(?:json)?\s*\n?/i', '', $content);
+    $content = (string)preg_replace('/\n?```\s*$/', '', $content);
+    // Drop only invalid markdown escapes; leave legitimate \n \" \\ \/ \t intact.
+    $content = (string)preg_replace('/\\\\([_*])/', '$1', $content);
+    $content = trim($content);
+
+    $decoded = json_decode($content, true);
+    if (is_array($decoded)) {
+        return $decoded;
+    }
+
+    // Collect every balanced top-level {...} block (ignoring braces inside JSON
+    // strings), then try the longest first — handles "prose then appended JSON".
+    $candidates = [];
+    $depth = 0;
+    $start = -1;
+    $inStr = false;
+    $escaped = false;
+    $len = strlen($content);
+    for ($i = 0; $i < $len; $i++) {
+        $ch = $content[$i];
+        if ($inStr) {
+            if ($escaped) {
+                $escaped = false;
+            } elseif ($ch === '\\') {
+                $escaped = true;
+            } elseif ($ch === '"') {
+                $inStr = false;
+            }
+            continue;
+        }
+        if ($ch === '"') {
+            $inStr = true;
+        } elseif ($ch === '{') {
+            if ($depth === 0) {
+                $start = $i;
+            }
+            $depth++;
+        } elseif ($ch === '}') {
+            if ($depth > 0) {
+                $depth--;
+                if ($depth === 0 && $start >= 0) {
+                    $candidates[] = substr($content, $start, $i - $start + 1);
+                    $start = -1;
+                }
+            }
+        }
+    }
+    usort($candidates, static fn(string $a, string $b): int => strlen($b) <=> strlen($a));
+    foreach ($candidates as $candidate) {
+        $decoded = json_decode($candidate, true);
+        if (is_array($decoded)) {
+            return $decoded;
+        }
+    }
+    return null;
+}
+
+/**
+ * Parse a labelled-prose reply (`answer: ...`, `what_we_found: ...`) into an assoc
+ * array keyed by $keys, for fine-tunes that ignore the JSON contract. Tolerates
+ * markdown-escaped key names (`what\_we\_found`). Each value runs until the next
+ * known key label or a trailing { JSON blob (discarded). Returns only found keys.
+ */
+function dbnToolsParseLabeledFields(string $text, array $keys): array
+{
+    $text = (string)preg_replace('/\\\\([_*])/', '$1', trim($text));
+    if ($text === '' || empty($keys)) {
+        return [];
+    }
+    // Find each "key:" label position (line start, case-insensitive).
+    $labels = [];
+    foreach ($keys as $key) {
+        if (preg_match('/^\s*' . preg_quote($key, '/') . '\s*:/im', $text, $m, PREG_OFFSET_CAPTURE)) {
+            $labelStart = $m[0][1];
+            $valueStart = $labelStart + strlen($m[0][0]);
+            $labels[] = ['key' => $key, 'start' => $labelStart, 'value_start' => $valueStart];
+        }
+    }
+    if (!$labels) {
+        return [];
+    }
+    usort($labels, static fn(array $a, array $b): int => $a['start'] <=> $b['start']);
+
+    $out = [];
+    $count = count($labels);
+    for ($i = 0; $i < $count; $i++) {
+        $end = ($i + 1 < $count) ? $labels[$i + 1]['start'] : strlen($text);
+        $value = substr($text, $labels[$i]['value_start'], $end - $labels[$i]['value_start']);
+        // Drop a trailing appended JSON blob from the last field's value.
+        $brace = strpos($value, '{');
+        if ($brace !== false && $i + 1 === $count) {
+            $value = substr($value, 0, $brace);
+        }
+        // Collapse a duplicated "key:" prefix the model sometimes repeats inside the value.
+        $value = (string)preg_replace('/^\s*' . preg_quote($labels[$i]['key'], '/') . '\s*:\s*/i', '', trim($value));
+        $out[$labels[$i]['key']] = trim($value);
+    }
+    return $out;
+}
+
 function dbnToolsInferCheckSeverity(string $text): string
 {
     if (preg_match('/ugyldig|§\s*41|kontradiksjon|klar nødvendighet|strand lobben|biologiske bånd/i', $text)) {