refactor: remove unused bd pin/unpin/hook commands (bd-x0zl)

Analysis found these commands are dead code:
- gt never calls `bd pin` - uses `bd update --status=pinned` instead
- Beads.Pin() wrapper exists but is never called
- bd hook functionality duplicated by gt mol status
- Code comment says "pinned field is cosmetic for bd hook visibility"

Removed:
- cmd/bd/pin.go
- cmd/bd/unpin.go
- cmd/bd/hook.go

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

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

internal/storage/storage_test.go

@@ -89,7 +89,7 @@ func (m *mockStorage) GetIssuesByLabel(ctx context.Context, label string) ([]*ty
 func (m *mockStorage) GetReadyWork(ctx context.Context, filter types.WorkFilter) ([]*types.Issue, error) {
 	return nil, nil
 }
-func (m *mockStorage) GetBlockedIssues(ctx context.Context) ([]*types.BlockedIssue, error) {
+func (m *mockStorage) GetBlockedIssues(ctx context.Context, filter types.WorkFilter) ([]*types.BlockedIssue, error) {
 	return nil, nil
 }
 func (m *mockStorage) GetEpicsEligibleForClosure(ctx context.Context) ([]*types.EpicStatus, error) {
@@ -98,6 +98,9 @@ func (m *mockStorage) GetEpicsEligibleForClosure(ctx context.Context) ([]*types.
 func (m *mockStorage) GetStaleIssues(ctx context.Context, filter types.StaleFilter) ([]*types.Issue, error) {
 	return nil, nil
 }
+func (m *mockStorage) GetNewlyUnblockedByClose(ctx context.Context, closedIssueID string) ([]*types.Issue, error) {
+	return nil, nil
+}
 func (m *mockStorage) AddComment(ctx context.Context, issueID, actor, comment string) error {
 	return nil
 }