feat: simplify mail wisps - single DB with --wisp flag (gt-fgms)

Removed dual-routing architecture that used separate .beads-wisp/ directory.
Now uses single .beads/ with --wisp flag passed to bd create.

Changes:
- router.go: Remove resolveWispDir(), simplify shouldBeWisp()
- mailbox.go: Remove wispDir field and dual-source query logic
- types.go: Rename Ephemeral to Wisp, remove MessageSource
- mail.go: Rename --ephemeral to --wisp flag
- spawn.go: Use Wisp field for lifecycle messages

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

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

internal/cmd/mail.go

@@ -22,7 +22,7 @@ var (
 	mailPriority      int
 	mailUrgent        bool
 	mailPinned        bool
-	mailEphemeral     bool
+	mailWisp          bool
 	mailType          string
 	mailReplyTo       string
 	mailNotify        bool
@@ -236,7 +236,7 @@ func init() {
 	mailSendCmd.Flags().StringVar(&mailReplyTo, "reply-to", "", "Message ID this is replying to")
 	mailSendCmd.Flags().BoolVarP(&mailNotify, "notify", "n", false, "Send tmux notification to recipient")
 	mailSendCmd.Flags().BoolVar(&mailPinned, "pinned", false, "Pin message (for handoff context that persists)")
-	mailSendCmd.Flags().BoolVar(&mailEphemeral, "ephemeral", false, "Send as ephemeral wisp (auto-cleanup on patrol squash)")
+	mailSendCmd.Flags().BoolVar(&mailWisp, "wisp", false, "Send as wisp (ephemeral, auto-cleanup on patrol squash)")
 	mailSendCmd.Flags().BoolVar(&mailSendSelf, "self", false, "Send to self (auto-detect from cwd)")
 	_ = mailSendCmd.MarkFlagRequired("subject")
 
@@ -334,8 +334,8 @@ func runMailSend(cmd *cobra.Command, args []string) error {
 	// Set pinned flag
 	msg.Pinned = mailPinned
 
-	// Set ephemeral flag
-	msg.Ephemeral = mailEphemeral
+	// Set wisp flag (ephemeral message)
+	msg.Wisp = mailWisp
 
 	// Handle reply-to: auto-set type to reply and look up thread
 	if mailReplyTo != "" {
@@ -439,12 +439,12 @@ func runMailInbox(cmd *cobra.Command, args []string) error {
 		if msg.Priority == mail.PriorityHigh || msg.Priority == mail.PriorityUrgent {
 			priorityMarker = " " + style.Bold.Render("!")
 		}
-		ephemeralMarker := ""
-		if msg.Ephemeral || msg.Source == mail.SourceWisp {
-			ephemeralMarker = " " + style.Dim.Render("(ephemeral)")
+		wispMarker := ""
+		if msg.Wisp {
+			wispMarker = " " + style.Dim.Render("(wisp)")
 		}
 
-		fmt.Printf("  %s %s%s%s%s\n", readMarker, msg.Subject, typeMarker, priorityMarker, ephemeralMarker)
+		fmt.Printf("  %s %s%s%s%s\n", readMarker, msg.Subject, typeMarker, priorityMarker, wispMarker)
 		fmt.Printf("    %s from %s\n",
 			style.Dim.Render(msg.ID),
 			msg.From)

internal/cmd/spawn.go

@@ -398,11 +398,11 @@ func runSpawn(cmd *cobra.Command, args []string) error {
 	// Notify Witness with POLECAT_STARTED message (ephemeral - lifecycle ping)
 	witnessAddr := fmt.Sprintf("%s/witness", rigName)
 	witnessNotification := &mail.Message{
-		To:        witnessAddr,
-		From:      sender,
-		Subject:   fmt.Sprintf("POLECAT_STARTED %s", polecatName),
-		Body:      fmt.Sprintf("Issue: %s\nSession: %s", assignmentID, sessionName),
-		Ephemeral: true,
+		To:      witnessAddr,
+		From:    sender,
+		Subject: fmt.Sprintf("POLECAT_STARTED %s", polecatName),
+		Body:    fmt.Sprintf("Issue: %s\nSession: %s", assignmentID, sessionName),
+		Wisp:    true,
 	}
 
 	if err := townRouter.Send(witnessNotification); err != nil {
@@ -414,11 +414,11 @@ func runSpawn(cmd *cobra.Command, args []string) error {
 	// Notify Deacon with POLECAT_STARTED message (ephemeral - lifecycle ping)
 	deaconAddr := "deacon/"
 	deaconNotification := &mail.Message{
-		To:        deaconAddr,
-		From:      sender,
-		Subject:   fmt.Sprintf("POLECAT_STARTED %s/%s", rigName, polecatName),
-		Body:      fmt.Sprintf("Issue: %s\nSession: %s", assignmentID, sessionName),
-		Ephemeral: true,
+		To:      deaconAddr,
+		From:    sender,
+		Subject: fmt.Sprintf("POLECAT_STARTED %s/%s", rigName, polecatName),
+		Body:    fmt.Sprintf("Issue: %s\nSession: %s", assignmentID, sessionName),
+		Wisp:    true,
 	}
 
 	if err := townRouter.Send(deaconNotification); err != nil {