feat(team): share leader memory with team members (read-only)

Team members dispatched via team tasks can now read the leader's memory
files (MEMORY.md, memory/*.md) as a fallback when they have no own
memory. Memory writes are blocked for members — only the leader can
save memory files. This follows the existing team_workspace context
propagation pattern: dispatch metadata → RunRequest → context → tools.

Affected tools: read_file (interceptor), memory_get, memory_search,
list_files (interceptor). All include leader fallback with per-user →
global scope cascade.

internal/tools/memory.go

@@ -98,10 +98,19 @@ func (t *MemorySearchTool) Execute(ctx context.Context, args map[string]any) *Re
 			searchOpts.MinScore = mc.MinScore
 		}
 	}
-	results, err := t.memStore.Search(ctx, query, agentID.String(), userID, searchOpts)
+	agentStr := agentID.String()
+	results, err := t.memStore.Search(ctx, query, agentStr, userID, searchOpts)
 	if err != nil {
 		return ErrorResult(fmt.Sprintf("memory search failed: %v", err))
 	}
+	// Fallback: also search leader's memory for team members and merge results.
+	if leaderID := LeaderAgentIDFromCtx(ctx); leaderID != "" && leaderID != agentStr {
+		leaderResults, lerr := t.memStore.Search(ctx, query, leaderID, userID, searchOpts)
+		if lerr != nil && userID != "" {
+			leaderResults, _ = t.memStore.Search(ctx, query, leaderID, "", searchOpts)
+		}
+		results = append(results, leaderResults...)
+	}
 	if len(results) == 0 {
 		return NewResult("No memory results found for query: " + query)
 	}
@@ -179,11 +188,21 @@ func (t *MemoryGetTool) Execute(ctx context.Context, args map[string]any) *Resul
 
 	userID := store.MemoryUserID(ctx)
 
+	agentStr := agentID.String()
+
 	// Try per-user first, then global
-	content, err := t.memStore.GetDocument(ctx, agentID.String(), userID, path)
+	content, err := t.memStore.GetDocument(ctx, agentStr, userID, path)
 	if err != nil && userID != "" {
-		// Fallback to global
-		content, err = t.memStore.GetDocument(ctx, agentID.String(), "", path)
+		content, err = t.memStore.GetDocument(ctx, agentStr, "", path)
+	}
+	// Fallback: try leader's memory for team members.
+	if err != nil {
+		if leaderID := LeaderAgentIDFromCtx(ctx); leaderID != "" && leaderID != agentStr {
+			content, err = t.memStore.GetDocument(ctx, leaderID, userID, path)
+			if err != nil && userID != "" {
+				content, err = t.memStore.GetDocument(ctx, leaderID, "", path)
+			}
+		}
 	}
 	if err != nil {
 		return ErrorResult(fmt.Sprintf("failed to read %s: %v", path, err))