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>

api/corpus-search.php

@@ -47,6 +47,46 @@ try {
         $catClause = $category !== null ? ' AND d.category = ?' : '';
         $excludeLike = '%' . EXCLUDED_DOMAIN . '%';
 
+        // Exact-identifier routing: the FULLTEXT tokenizer drops "§ 4-12" / "Art. 8"
+        // to stopword fragments, so a citation query never matches. Route those to a
+        // verbatim LIKE lookup and pin the hits ahead of the fuzzy BM25 results.
+        $exactHits = [];
+        $exactChunkIds = [];
+        $citationAtoms = DbnLegalToolsService::citationAtoms($query);
+        if (!empty($citationAtoms)) {
+            $atomClauses = [];
+            $atomParams  = [1];
+            foreach ($citationAtoms as $atom) {
+                $like = '%' . str_replace(['%', '_'], ['\\%', '\\_'], $atom) . '%';
+                $atomClauses[] = '(c.content LIKE ? OR c.section_title LIKE ?)';
+                $atomParams[]  = $like;
+                $atomParams[]  = $like;
+            }
+            $atomParams[] = $excludeLike;
+            $exactSql = "SELECT d.id AS document_id, d.title, d.category,
+                                d.source_url, c.id AS chunk_id, c.content AS excerpt,
+                                c.section_title AS section, d.language, 1.0 AS score
+                         FROM chunks c
+                         JOIN documents d ON c.document_id = d.id
+                         WHERE d.corpus_id = ? AND d.status = 'ready'
+                           AND (" . implode(' OR ', $atomClauses) . ")
+                           AND d.source_url NOT LIKE ?
+                         $catClause
+                         LIMIT $limit";
+            $exactParams = $atomParams;
+            if ($category !== null) $exactParams[] = $category;
+            try {
+                $stmt = $ragDb->prepare($exactSql);
+                $stmt->execute($exactParams);
+                foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $r) {
+                    $exactHits[] = $r;
+                    if (isset($r['chunk_id'])) $exactChunkIds[(int)$r['chunk_id']] = true;
+                }
+            } catch (Throwable $e) {
+                // Non-fatal — fall through to fuzzy BM25.
+            }
+        }
+
         // Try FULLTEXT index first
         try {
             $sql = "SELECT d.id AS document_id, d.title, d.category,
@@ -89,6 +129,12 @@ try {
             $rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
         }
 
+        // Exact identifier hits lead; drop fuzzy rows that duplicate them.
+        if (!empty($exactChunkIds)) {
+            $rows = array_values(array_filter($rows, fn($r) => empty($exactChunkIds[(int)($r['chunk_id'] ?? 0)])));
+        }
+        $rows = array_slice(array_merge($exactHits, $rows), 0, $limit);
+
         $hits = array_map(fn($r) => [
             'title'       => $r['title'] ?? '',
             'category'    => $r['category'] ?? '',
@@ -100,6 +146,7 @@ try {
             'chunk_id'    => isset($r['chunk_id']) ? (int)$r['chunk_id'] : null,
             'source_url'  => $r['source_url'] ?? null,
             'language'    => $r['language'] ?? null,
+            'exact_match' => !empty($exactChunkIds[(int)($r['chunk_id'] ?? 0)]),
         ], $rows);
         dbnToolsRespond(['ok' => true, 'hits' => $hits, 'mode' => 'bm25', 'query' => $query]);
     }