feat: add owner field for human attribution in HOP CV chains

Add 'owner' field to Issue struct for tracking the human responsible
for the issue, distinct from 'created_by' which tracks the executor.
Owner is populated from git author email (GIT_AUTHOR_EMAIL or git
config user.email), per Decision 008 for CV accumulation.

Changes:
- Add Owner field to types.Issue with omitempty JSON tag
- Include Owner in content hash computation
- Add owner column migration (036_owner_column.go)
- Update all SQL queries to include owner field
- Add getOwner() helper using git author email fallback chain
- Populate owner in bd create command
- Add owner to RPC CreateArgs protocol

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

Executed-By: beads/crew/dave
Rig: beads
Role: crew

internal/storage/sqlite/ready.go

@@ -152,7 +152,7 @@ func (s *SQLiteStorage) GetReadyWork(ctx context.Context, filter types.WorkFilte
 	query := fmt.Sprintf(`
 		SELECT i.id, i.content_hash, i.title, i.description, i.design, i.acceptance_criteria, i.notes,
 		i.status, i.priority, i.issue_type, i.assignee, i.estimated_minutes,
-		i.created_at, i.created_by, i.updated_at, i.closed_at, i.external_ref, i.source_repo, i.close_reason,
+		i.created_at, i.created_by, i.owner, i.updated_at, i.closed_at, i.external_ref, i.source_repo, i.close_reason,
 		i.deleted_at, i.deleted_by, i.delete_reason, i.original_type,
 		i.sender, i.ephemeral, i.pinned, i.is_template,
 		i.await_type, i.await_id, i.timeout_ns, i.waiters
@@ -744,7 +744,7 @@ func (s *SQLiteStorage) GetNewlyUnblockedByClose(ctx context.Context, closedIssu
 	query := `
 		SELECT i.id, i.content_hash, i.title, i.description, i.design, i.acceptance_criteria, i.notes,
 		       i.status, i.priority, i.issue_type, i.assignee, i.estimated_minutes,
-		       i.created_at, i.created_by, i.updated_at, i.closed_at, i.external_ref, i.source_repo, i.close_reason,
+		       i.created_at, i.created_by, i.owner, i.updated_at, i.closed_at, i.external_ref, i.source_repo, i.close_reason,
 		       i.deleted_at, i.deleted_by, i.delete_reason, i.original_type,
 		       i.sender, i.ephemeral, i.pinned, i.is_template,
 		       i.await_type, i.await_id, i.timeout_ns, i.waiters