feat: Implement no-tmux mode with beads as data plane (gt-vc3l4)

Enable Gas Town to operate without tmux by using beads for args transport:

- Add `attached_args` field to beads AttachmentFields
- gt sling: Store args in bead description, graceful fallback if no tmux
- gt prime: Display attached args prominently on startup
- gt mol status: Include attached_args in status output
- gt spawn --naked: Assign work via mail only, skip tmux session

Agents discover args via gt prime / bd show when starting manually.
Docs added explaining what works vs degraded behavior in no-tmux mode.

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

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

internal/cmd/molecule_status.go

@@ -35,6 +35,7 @@ type MoleculeStatusInfo struct {
 	PinnedBead       *beads.Issue          `json:"pinned_bead,omitempty"`
 	AttachedMolecule string                `json:"attached_molecule,omitempty"`
 	AttachedAt       string                `json:"attached_at,omitempty"`
+	AttachedArgs     string                `json:"attached_args,omitempty"`
 	IsWisp           bool                  `json:"is_wisp"`
 	Progress         *MoleculeProgressInfo `json:"progress,omitempty"`
 	NextAction       string                `json:"next_action,omitempty"`
@@ -264,6 +265,7 @@ func runMoleculeStatus(cmd *cobra.Command, args []string) error {
 		if attachment != nil {
 			status.AttachedMolecule = attachment.AttachedMolecule
 			status.AttachedAt = attachment.AttachedAt
+			status.AttachedArgs = attachment.AttachedArgs
 
 			// Check if it's a wisp (look for wisp indicator in description)
 			status.IsWisp = strings.Contains(pinnedBeads[0].Description, "wisp: true") ||
@@ -456,6 +458,9 @@ func outputMoleculeStatus(status MoleculeStatusInfo) error {
 		if status.AttachedAt != "" {
 			fmt.Printf("   Attached: %s\n", status.AttachedAt)
 		}
+		if status.AttachedArgs != "" {
+			fmt.Printf("   %s %s\n", style.Bold.Render("Args:"), status.AttachedArgs)
+		}
 	} else {
 		fmt.Printf("%s\n", style.Dim.Render("No molecule attached"))
 	}