feat(tui): add interactive run mode for checklists and fill mode for templates

Run mode (r key on checklist cards): cursor navigates steps, space
toggles done/undone, r resets all, esc saves changes to DB and exits.
Persists step state — improvement over web which discards on exit.

Fill mode (f key on template cards): tab/shift-tab navigates slots,
type to fill values, enter resolves template and copies to clipboard
with use count increment. Esc cancels without copying.

Both modes are sub-states of detail view, keeping architecture simple.

internal/tui/detail.go

@@ -11,11 +11,22 @@ import (
 	"github.com/lerko/nib/internal/display"
 )
 
+type detailMode int
+
+const (
+	detailPreview detailMode = iota
+	detailRun
+	detailFill
+)
+
 type detailModel struct {
 	entity *db.Entity
 	scroll int
 	height int
 	width  int
+	mode   detailMode
+	run    runModel
+	fill   fillModel
 }
 
 func newDetailModel() detailModel {
@@ -25,6 +36,7 @@ func newDetailModel() detailModel {
 func (d *detailModel) setEntity(e *db.Entity) {
 	d.entity = e
 	d.scroll = 0
+	d.mode = detailPreview
 }
 
 func (d *detailModel) setSize(width, height int) {
@@ -32,19 +44,40 @@ func (d *detailModel) setSize(width, height int) {
 	d.height = height
 }
 
-func (d detailModel) update(msg tea.KeyMsg) detailModel {
-	switch msg.String() {
-	case "up", "k":
-		if d.scroll > 0 {
-			d.scroll--
+func (d detailModel) update(msg tea.KeyMsg) (detailModel, tea.Cmd) {
+	switch d.mode {
+	case detailRun:
+		d.run = d.run.update(msg.String())
+		return d, nil
+	case detailFill:
+		var cmd tea.Cmd
+		d.fill, cmd = d.fill.update(msg)
+		return d, cmd
+	default:
+		switch msg.String() {
+		case "up", "k":
+			if d.scroll > 0 {
+				d.scroll--
+			}
+		case "down", "j":
+			d.scroll++
 		}
-	case "down", "j":
-		d.scroll++
+		return d, nil
 	}
-	return d
 }
 
 func (d detailModel) view(width int) string {
+	switch d.mode {
+	case detailRun:
+		return d.run.view(width)
+	case detailFill:
+		return d.fill.view(width)
+	default:
+		return d.previewView(width)
+	}
+}
+
+func (d detailModel) previewView(width int) string {
 	if d.entity == nil {
 		return ""
 	}
@@ -154,6 +187,7 @@ func renderCardData(e *db.Entity) string {
 		}
 		progress := fmt.Sprintf("  %d/%d steps", done, len(steps))
 		b.WriteString(detailLabelStyle.Render(progress))
+		b.WriteString("  " + helpStyle.Render("r:run"))
 
 	case db.CardTemplate:
 		slots, ok := data["slots"].([]interface{})
@@ -174,6 +208,7 @@ func renderCardData(e *db.Entity) string {
 			}
 			b.WriteString(line + "\n")
 		}
+		b.WriteString("  " + helpStyle.Render("f:fill"))
 
 	case db.CardDecision:
 		if chose, ok := data["chose"].(string); ok && chose != "" {