feat(rpc): enrich MutationEvent with Title and Assignee fields

Add Title and Assignee fields to MutationEvent struct so activity feeds
can display meaningful context without extra lookups. Updated emitMutation
signature to accept these values and modified all callers:

- Create: passes issue.Title and issue.Assignee directly
- Update/Close: moved emitMutation after GetIssue to access enriched data
- Delete: uses existing issue lookup before deletion
- Dep/Label/Comment ops: passes empty strings (would require extra lookup)

Fixes bd-gqxd

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

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

internal/rpc/server_core.go

@@ -80,6 +80,8 @@ const (
 type MutationEvent struct {
 	Type      string    // One of the Mutation* constants
 	IssueID   string    // e.g., "bd-42"
+	Title     string    // Issue title for display context (may be empty for some operations)
+	Assignee  string    // Issue assignee for display context (may be empty)
 	Timestamp time.Time
 	// Optional metadata for richer events (used by status, bonded, etc.)
 	OldStatus string `json:"old_status,omitempty"` // Previous status (for status events)
@@ -138,10 +140,13 @@ func NewServer(socketPath string, store storage.Storage, workspacePath string, d
 // emitMutation sends a mutation event to the daemon's event-driven loop.
 // Non-blocking: drops event if channel is full (sync will happen eventually).
 // Also stores in recent mutations buffer for polling.
-func (s *Server) emitMutation(eventType, issueID string) {
+// Title and assignee provide context for activity feeds; pass empty strings if unknown.
+func (s *Server) emitMutation(eventType, issueID, title, assignee string) {
 	s.emitRichMutation(MutationEvent{
-		Type:    eventType,
-		IssueID: issueID,
+		Type:     eventType,
+		IssueID:  issueID,
+		Title:    title,
+		Assignee: assignee,
 	})
 }