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/commands.go

@@ -49,6 +49,10 @@ type absorbSourcesLoadedMsg struct {
 	entities []*db.Entity
 }
 
+type stepsPersistedMsg struct{}
+
+type templateCopiedMsg struct{}
+
 type tagsLoadedMsg struct {
 	tags []db.TagCount
 }
@@ -235,3 +239,25 @@ func absorbEntity(store *db.Store, targetID, sourceID string) tea.Cmd {
 		return entityAbsorbedMsg{targetID}
 	}
 }
+
+func persistSteps(store *db.Store, entityID string, stepsJSON string) tea.Cmd {
+	return func() tea.Msg {
+		update := db.EntityUpdate{CardData: &stepsJSON}
+		if err := store.Update(entityID, &update); err != nil {
+			return errMsg{err}
+		}
+		return stepsPersistedMsg{}
+	}
+}
+
+func copyResolved(store *db.Store, entityID string, resolved string) tea.Cmd {
+	return func() tea.Msg {
+		if err := clipboard.WriteAll(resolved); err != nil {
+			return errMsg{err}
+		}
+		if err := store.IncrementUse(entityID); err != nil {
+			return errMsg{err}
+		}
+		return templateCopiedMsg{}
+	}
+}