Make dbn-legal-agent-v3 checker context-aware; wire into LegalAnalysisAgent

Three fixes:
1. bootstrap.php dbnToolsRunLegalCheck(): prepend first 350 chars of synthesis text
   to the v3 user message so it validates actual content, not just general law.
2. BvjAnalyzerAgent: fix engine guard — was skipping check for claude_sonnet/haiku;
   now skips only when dbn_legal_v3 is the synthesis model (it already IS the check).
3. LegalAnalysisAgent: add post-synthesis dbnToolsRunLegalCheck() call after Pass 3;
   add 'legal_check' key to runFullAnalysis() return.

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

includes/LegalAnalysisAgent.php

@@ -362,6 +362,15 @@ PROMPT;
         $emit('progress', ['step' => 'synthesising', 'detail' => 'Synthesising overall assessment…']);
         $synth = $this->synthesise($answered, $language, $docType);
 
+        // Post-synthesis legal check — dbn-legal-agent-v3 validates the overall assessment
+        $legalCheck = [];
+        try {
+            $legalCheck = dbnToolsRunLegalCheck(
+                mb_strimwidth($synth['overall_assessment'], 0, 800),
+                $docType
+            );
+        } catch (Throwable) {}
+
         return [
             'ok'                 => true,
             'issues'             => $answered,
@@ -370,6 +379,7 @@ PROMPT;
             'disclaimer'         => $synth['disclaimer'],
             'doc_type'           => $docType,
             'model'              => self::LEGAL_MODEL,
+            'legal_check'        => $legalCheck,
             'latency_ms'         => (int)round(microtime(true) * 1000) - $startMs,
         ];
     }