Fix daemon/direct mode inconsistency in graph commands (bd-fu83)

Commands relate, unrelate, duplicate, and supersede now properly
use RPC Update when daemonClient is available, instead of always
calling store.UpdateIssue() directly and bypassing the daemon.

Added RelatesTo, DuplicateOf, and SupersededBy fields to UpdateArgs
in the RPC protocol, and updated server_issues_epics.go to handle them.

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

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

internal/rpc/protocol.go

@@ -99,6 +99,10 @@ type UpdateArgs struct {
 	Sender    *string `json:"sender,omitempty"`     // Who sent this (for messages)
 	Ephemeral *bool   `json:"ephemeral,omitempty"`  // Can be bulk-deleted when closed
 	RepliesTo *string `json:"replies_to,omitempty"` // Issue ID for conversation threading
+	// Graph link fields (bd-fu83)
+	RelatesTo    *string `json:"relates_to,omitempty"`    // JSON array of related issue IDs
+	DuplicateOf  *string `json:"duplicate_of,omitempty"`  // Canonical issue ID if duplicate
+	SupersededBy *string `json:"superseded_by,omitempty"` // Replacement issue ID if obsolete
 }
 
 // CloseArgs represents arguments for the close operation

internal/rpc/server_issues_epics.go

@@ -87,6 +87,16 @@ func updatesFromArgs(a UpdateArgs) map[string]interface{} {
 	if a.RepliesTo != nil {
 		u["replies_to"] = *a.RepliesTo
 	}
+	// Graph link fields (bd-fu83)
+	if a.RelatesTo != nil {
+		u["relates_to"] = *a.RelatesTo
+	}
+	if a.DuplicateOf != nil {
+		u["duplicate_of"] = *a.DuplicateOf
+	}
+	if a.SupersededBy != nil {
+		u["superseded_by"] = *a.SupersededBy
+	}
 	return u
 }