feat: Make relates_to and duplicates links bidirectional

- relates_to and duplicates now create reverse links automatically
- task_show displays Related and Duplicates sections
- blocks remains unidirectional (A blocks B, B is blocked by A)

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

src/tools/crud.ts

@@ -195,6 +195,36 @@ export async function taskShow(id: string): Promise<string> {
     }
   }
 
+  // Get related tasks (bidirectional - only need to query one direction since links are symmetric)
+  const relatesTo = await query<{ id: string; title: string }>(
+    `SELECT t.id, t.title FROM task_links l
+     JOIN tasks t ON t.id = l.to_task_id
+     WHERE l.from_task_id = $1 AND l.link_type = 'relates_to'`,
+    [id]
+  );
+
+  if (relatesTo.length > 0) {
+    output += `\n**Related:**\n`;
+    for (const t of relatesTo) {
+      output += `  - ${t.id}: ${t.title}\n`;
+    }
+  }
+
+  // Get duplicates (bidirectional)
+  const duplicates = await query<{ id: string; title: string }>(
+    `SELECT t.id, t.title FROM task_links l
+     JOIN tasks t ON t.id = l.to_task_id
+     WHERE l.from_task_id = $1 AND l.link_type = 'duplicates'`,
+    [id]
+  );
+
+  if (duplicates.length > 0) {
+    output += `\n**Duplicates:**\n`;
+    for (const t of duplicates) {
+      output += `  - ${t.id}: ${t.title}\n`;
+    }
+  }
+
   return output;
 }