refactor: ApprovalKind::as_str owns the kind→string mapping

replaces three hand-rolled six-arm matches (actions.rs ×2,
state_snapshot.rs); approvals::kind_to_str delegates. a new kind can
no longer silently miss one of them

hive-c0re/src/approvals.rs

@@ -411,18 +411,11 @@ fn row_to_approval(row: &rusqlite::Row<'_>) -> rusqlite::Result<Approval> {
 }
 
 /// Stable kind→str mapping used wherever we emit `ApprovalResolved`
-/// or persist a kind to sqlite. `pub(crate)` so callers like
-/// `questions::handle_cancel_loose_end` don't have to duplicate the
-/// match; bumping a kind here is the single source of truth.
+/// or persist a kind to sqlite. Thin alias over
+/// [`ApprovalKind::as_str`] (the wire-type owns the mapping) kept for
+/// the existing call sites' name.
 pub(crate) fn kind_to_str(kind: ApprovalKind) -> &'static str {
-    match kind {
-        ApprovalKind::ApplyCommit => "apply_commit",
-        ApprovalKind::Spawn => "spawn",
-        ApprovalKind::InitConfig => "init_config",
-        ApprovalKind::UpdateMetaInputs => "update_meta_inputs",
-        ApprovalKind::SchedulePrompt => "schedule_prompt",
-        ApprovalKind::MergeConfigPr => "merge_config_pr",
-    }
+    kind.as_str()
 }
 
 fn kind_from_str(s: &str) -> Result<ApprovalKind> {