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/help.go

@@ -35,6 +35,20 @@ func renderHelp(width, height int) string {
 			{"c", "copy to clipboard"},
 			{"e", "edit in $EDITOR"},
 			{"!", "toggle pin"},
+			{"r", "run checklist"},
+			{"f", "fill template"},
+		}},
+		{"Run Mode", [][2]string{
+			{"j/k", "move between steps"},
+			{"space", "toggle step"},
+			{"r", "reset all steps"},
+			{"esc", "save + exit"},
+		}},
+		{"Fill Mode", [][2]string{
+			{"tab", "next slot"},
+			{"shift+tab", "prev slot"},
+			{"enter", "copy resolved"},
+			{"esc", "cancel"},
 		}},
 		{"Global", [][2]string{
 			{"?", "toggle help"},