Fix CF-271: Add fallback text search to archive_search

When LiteLLM embedding service is unavailable, archive_search now gracefully falls back to PostgreSQL text search (ILIKE) instead of returning an error. Also adds dotenv support for proper credential loading.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/tools/archives.ts

@@ -125,10 +125,54 @@ export async function archiveSearch(args: ArchiveSearchArgs): Promise<string> {
   // Generate embedding for search
   const embedding = await getEmbedding(searchQuery);
 
+  // Fallback to text search if embeddings unavailable
   if (!embedding) {
-    return 'Error: Could not generate embedding for search';
+    console.warn('Embeddings unavailable, falling back to text search');
+
+    let whereClause = '(title ILIKE $1 OR content ILIKE $1)';
+    const params: unknown[] = [`%${searchQuery}%`];
+    let paramIndex = 2;
+
+    if (project) {
+      whereClause += ` AND project_key = $${paramIndex++}`;
+      params.push(project);
+    }
+    if (archive_type) {
+      whereClause += ` AND archive_type = $${paramIndex++}`;
+      params.push(archive_type);
+    }
+
+    params.push(limit);
+
+    const archives = await query<Archive>(
+      `SELECT id, archive_type, title, original_path, file_size,
+              to_char(archived_at, 'YYYY-MM-DD') as archived_at
+       FROM project_archives
+       WHERE ${whereClause}
+       ORDER BY archived_at DESC
+       LIMIT $${paramIndex}`,
+      params
+    );
+
+    if (archives.length === 0) {
+      return 'No relevant archives found';
+    }
+
+    const lines = ['Relevant archives (text search - embeddings unavailable):\n'];
+    for (const a of archives) {
+      const sizeStr = a.file_size ? ` (${Math.round(a.file_size / 1024)}KB)` : '';
+      lines.push(`**[${a.archive_type}]** ${a.title}`);
+      lines.push(`  Archived: ${a.archived_at}${sizeStr}`);
+      if (a.original_path) {
+        lines.push(`  Path: ${a.original_path}`);
+      }
+      lines.push('');
+    }
+
+    return lines.join('\n');
   }
 
+  // Semantic search with embeddings
   const embeddingStr = formatEmbedding(embedding);
 
   let whereClause = 'WHERE embedding IS NOT NULL';