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

cmd/bd/create.go

@@ -199,6 +199,7 @@ var createCmd = &cobra.Command{
 				ExternalRef:        externalRefPtr,
 				Ephemeral:          wisp,
 				CreatedBy:          getActorWithGit(),
+				Owner:              getOwner(),
 				MolType:            molType,
 				RoleType:           roleType,
 				Rig:                agentRig,
@@ -423,6 +424,7 @@ var createCmd = &cobra.Command{
 				WaitsForGate:       waitsForGate,
 				Ephemeral:          wisp,
 				CreatedBy:          getActorWithGit(),
+				Owner:              getOwner(),
 				MolType:            string(molType),
 				RoleType:           roleType,
 				Rig:                agentRig,
@@ -482,6 +484,7 @@ var createCmd = &cobra.Command{
 			EstimatedMinutes:   estimatedMinutes,
 			Ephemeral:          wisp,
 			CreatedBy:          getActorWithGit(),
+			Owner:              getOwner(),
 			MolType:            molType,
 			RoleType:           roleType,
 			Rig:                agentRig,
@@ -808,6 +811,7 @@ func createInRig(cmd *cobra.Command, rigName, title, description, issueType stri
 		ExternalRef:        externalRefPtr,
 		Ephemeral:          wisp,
 		CreatedBy:          getActorWithGit(),
+		Owner:              getOwner(),
 		// Event fields (bd-xwvo fix)
 		EventKind: eventCategory,
 		Actor:     eventActor,