Fix #202: Add dependency_type to bd show --json output (#203)

The JSON output from bd show now includes the dependency_type field
for both dependencies and dependents, enabling programmatic
differentiation between dependency types (blocks, related,
parent-child, discovered-from).

Implementation approach:
- Added IssueWithDependencyMetadata type with embedded Issue and
  DependencyType field
- Extended GetDependenciesWithMetadata and GetDependentsWithMetadata
  to include dependency type from SQL JOIN
- Made GetDependencies and GetDependents wrap the WithMetadata
  methods for backward compatibility
- Added scanIssuesWithDependencyType helper to handle scanning with
  dependency type field
- Updated bd show --json to use WithMetadata methods

Tests added:
- TestGetDependenciesWithMetadata - basic functionality
- TestGetDependentsWithMetadata - dependent retrieval
- TestGetDependenciesWithMetadataEmpty - edge case handling
- TestGetDependenciesWithMetadataMultipleTypes - multiple types

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Happy <yesreply@happy.engineering>

internal/types/types.go

@@ -153,6 +153,13 @@ type DependencyCounts struct {
 	DependentCount  int `json:"dependent_count"`  // Number of issues that depend on this issue
 }
 
+// IssueWithDependencyMetadata extends Issue with dependency relationship type
+// Note: We explicitly include all Issue fields to ensure proper JSON marshaling
+type IssueWithDependencyMetadata struct {
+	Issue
+	DependencyType DependencyType `json:"dependency_type"`
+}
+
 // IssueWithCounts extends Issue with dependency relationship counts
 type IssueWithCounts struct {
 	*Issue