feat(mcp): expose corpus_search, korrespond_refine, extract_text tools

Restores the 3 tools (manifest + invoke arms + invokeExtract helper),
the citation-atom RAG lever in LegalTools/corpus-search, and the catalog
icons. These were live on prod via rsync but uncommitted, so a git-pull
deploy reverted the manifest from 22 to 19 tools.

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

mcp.php

@@ -25,6 +25,7 @@ $toolCatalog = DbnMcpRuntime::tools();
 
 $toolIcons = [
     'dbn.search_legal'        => '🔍',
+    'dbn.corpus_search'       => '🧭',
     'dbn.ask'                 => '💬',
     'dbn.summarize'           => '📋',
     'dbn.timeline'            => '📅',
@@ -32,11 +33,13 @@ $toolIcons = [
     'dbn.translate'           => '🌍',
     'dbn.legal_analysis'      => '⚖️',
     'dbn.korrespond'          => '✉️',
+    'dbn.korrespond_refine'   => '✨',
     'dbn.barnevernet_analyze' => '📄',
     'dbn.advocate_brief'      => '🏛️',
     'dbn.deep_research'       => '🔬',
     'dbn.discrepancy_find'    => '🔄',
     'dbn.transcribe_audio'    => '🎤',
+    'dbn.extract_text'        => '📑',
     'dbn.corpus_stats'        => '📊',
     'dbn.list_documents'      => '📚',
     'dbn.get_document'        => '📖',