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-sh4re/src/lib.rs

@@ -250,6 +250,24 @@ pub enum ApprovalKind {
     MergeConfigPr,
 }
 
+impl ApprovalKind {
+    /// Wire/UI string — the same value serde's `snake_case` rename
+    /// produces. The single source of truth for every place that needs
+    /// the kind as a `&'static str` (sqlite storage, dashboard events),
+    /// so adding a variant can't silently miss a hand-rolled match.
+    #[must_use]
+    pub fn as_str(self) -> &'static str {
+        match self {
+            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",
+        }
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 #[serde(rename_all = "snake_case")]
 pub enum ApprovalStatus {