Phase 1: add saveState — persist ExtensionState via appendEntry.

STATE_ENTRY_TYPE skill-reinject:state matches SPEC §6.1 so state survives
/resume and branch reload without a full rescan.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/state.ts

@@ -1,3 +1,5 @@
+import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
+
 /** How a skill was first observed in the session (SPEC §6.2). */
 export type SkillSource = "slash" | "skill-block" | "read";
 
@@ -31,6 +33,12 @@ export interface RuntimeFlags {
 	autoCompactIntegration: AutoCompactIntegration;
 }
 
+export const STATE_ENTRY_TYPE = "skill-reinject:state";
+
+export function saveState(pi: ExtensionAPI, state: ExtensionState): void {
+	pi.appendEntry<ExtensionState>(STATE_ENTRY_TYPE, state);
+}
+
 export function createInitialState(): ExtensionState {
 	return {
 		version: 1,