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/types/types.go

@@ -368,6 +368,7 @@ const (
 	DepBlocks            DependencyType = "blocks"
 	DepParentChild       DependencyType = "parent-child"
 	DepConditionalBlocks DependencyType = "conditional-blocks" // B runs only if A fails (bd-kzda)
+	DepWaitsFor          DependencyType = "waits-for"          // Fanout gate: wait for dynamic children (bd-xo1o.2)
 
 	// Association types
 	DepRelated        DependencyType = "related"
@@ -396,7 +397,7 @@ func (d DependencyType) IsValid() bool {
 // Returns false for custom/user-defined types (which are still valid).
 func (d DependencyType) IsWellKnown() bool {
 	switch d {
-	case DepBlocks, DepParentChild, DepConditionalBlocks, DepRelated, DepDiscoveredFrom,
+	case DepBlocks, DepParentChild, DepConditionalBlocks, DepWaitsFor, DepRelated, DepDiscoveredFrom,
 		DepRepliesTo, DepRelatesTo, DepDuplicates, DepSupersedes,
 		DepAuthoredBy, DepAssignedTo, DepApprovedBy:
 		return true
@@ -405,11 +406,27 @@ func (d DependencyType) IsWellKnown() bool {
 }
 
 // AffectsReadyWork returns true if this dependency type blocks work.
-// Only "blocks", "parent-child", and "conditional-blocks" affect the ready work calculation.
+// Only blocking types affect the ready work calculation.
 func (d DependencyType) AffectsReadyWork() bool {
-	return d == DepBlocks || d == DepParentChild || d == DepConditionalBlocks
+	return d == DepBlocks || d == DepParentChild || d == DepConditionalBlocks || d == DepWaitsFor
 }
 
+// WaitsForMeta holds metadata for waits-for dependencies (fanout gates).
+// Stored as JSON in the Dependency.Metadata field.
+type WaitsForMeta struct {
+	// Gate type: "all-children" (wait for all), "any-children" (wait for first)
+	Gate string `json:"gate"`
+	// SpawnerID identifies which step/issue spawns the children to wait for.
+	// If empty, waits for all direct children of the depends_on_id issue.
+	SpawnerID string `json:"spawner_id,omitempty"`
+}
+
+// WaitsForGate constants
+const (
+	WaitsForAllChildren = "all-children" // Wait for all dynamic children to complete
+	WaitsForAnyChildren = "any-children" // Proceed when first child completes (future)
+)
+
 // FailureCloseKeywords are keywords that indicate an issue was closed due to failure.
 // Used by conditional-blocks dependencies to determine if the condition is met.
 var FailureCloseKeywords = []string{

internal/types/types_test.go

@@ -483,6 +483,7 @@ func TestDependencyTypeAffectsReadyWork(t *testing.T) {
 		{DepBlocks, true},
 		{DepParentChild, true},
 		{DepConditionalBlocks, true},
+		{DepWaitsFor, true},
 		{DepRelated, false},
 		{DepDiscoveredFrom, false},
 		{DepRepliesTo, false},