feat: add waits-for dependency type for fanout gates (bd-xo1o.2)

Adds 'waits-for' dependency type for dynamic molecule bonding:
- DepWaitsFor blocks an issue until spawner's children are closed
- Two gate types: all-children (wait for all) or any-children (first)
- Updated blocked_cache.go CTE to handle waits-for dependencies
- Added --waits-for and --waits-for-gate flags to bd create command
- Added WaitsForMeta struct for gate metadata storage
- Full test coverage for all gate types and dynamic child scenarios

This enables patrol molecules to wait for dynamically-bonded arms to
complete before proceeding (Christmas Ornament pattern).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/rpc/protocol.go

@@ -72,6 +72,9 @@ type CreateArgs struct {
 	EstimatedMinutes   *int     `json:"estimated_minutes,omitempty"` // Time estimate in minutes
 	Labels             []string `json:"labels,omitempty"`
 	Dependencies       []string `json:"dependencies,omitempty"`
+	// Waits-for dependencies (bd-xo1o.2)
+	WaitsFor     string `json:"waits_for,omitempty"`      // Spawner issue ID to wait for
+	WaitsForGate string `json:"waits_for_gate,omitempty"` // Gate type: all-children or any-children
 	// Messaging fields (bd-kwro)
 	Sender string `json:"sender,omitempty"` // Who sent this (for messages)
 	Wisp   bool   `json:"wisp,omitempty"`   // Wisp = ephemeral vapor from the Steam Engine; bulk-deleted when closed

internal/rpc/server_issues_epics.go

@@ -309,6 +309,46 @@ func (s *Server) handleCreate(req *Request) Response {
 		}
 	}
 
+	// Add waits-for dependency if specified (bd-xo1o.2)
+	if createArgs.WaitsFor != "" {
+		// Validate gate type
+		gate := createArgs.WaitsForGate
+		if gate == "" {
+			gate = types.WaitsForAllChildren
+		}
+		if gate != types.WaitsForAllChildren && gate != types.WaitsForAnyChildren {
+			return Response{
+				Success: false,
+				Error:   fmt.Sprintf("invalid waits_for_gate value '%s' (valid: all-children, any-children)", gate),
+			}
+		}
+
+		// Create metadata JSON
+		meta := types.WaitsForMeta{
+			Gate: gate,
+		}
+		metaJSON, err := json.Marshal(meta)
+		if err != nil {
+			return Response{
+				Success: false,
+				Error:   fmt.Sprintf("failed to serialize waits-for metadata: %v", err),
+			}
+		}
+
+		dep := &types.Dependency{
+			IssueID:     issue.ID,
+			DependsOnID: createArgs.WaitsFor,
+			Type:        types.DepWaitsFor,
+			Metadata:    string(metaJSON),
+		}
+		if err := store.AddDependency(ctx, dep, s.reqActor(req)); err != nil {
+			return Response{
+				Success: false,
+				Error:   fmt.Sprintf("failed to add waits-for dependency %s -> %s: %v", issue.ID, createArgs.WaitsFor, err),
+			}
+		}
+	}
+
 	// Emit mutation event for event-driven daemon
 	s.emitMutation(MutationCreate, issue.ID)