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;
 }
 

src/tools/relations.ts

@@ -20,11 +20,15 @@ interface ChecklistToggleArgs {
 
 /**
  * Create a dependency between tasks
+ * - blocks: unidirectional (A blocks B)
+ * - relates_to: bidirectional (A relates to B = B relates to A)
+ * - duplicates: bidirectional (A duplicates B = B duplicates A)
  */
 export async function taskLink(args: TaskLinkArgs): Promise<string> {
   const { from_id, to_id, link_type } = args;
 
   try {
+    // Create the primary link
     await execute(
       `INSERT INTO task_links (from_task_id, to_task_id, link_type)
        VALUES ($1, $2, $3)
@@ -32,6 +36,16 @@ export async function taskLink(args: TaskLinkArgs): Promise<string> {
       [from_id, to_id, link_type]
     );
 
+    // For symmetric relationships, create reverse link
+    if (link_type === 'relates_to' || link_type === 'duplicates') {
+      await execute(
+        `INSERT INTO task_links (from_task_id, to_task_id, link_type)
+         VALUES ($1, $2, $3)
+         ON CONFLICT (from_task_id, to_task_id, link_type) DO NOTHING`,
+        [to_id, from_id, link_type]
+      );
+    }
+
     return `Linked: ${from_id} ${link_type} ${to_id}`;
   } catch (error) {
     return `Error creating link: ${error}`;