fix(plugin): normalize event session ids

Handle OpenCode session events that carry the session ID under properties.info.id or properties.info.sessionID so background tasks and continuation hooks do not miss idle/error/delete events.

Add regression coverage for nested session.idle events completing background tasks and waking continuation hooks.

src/hooks/rules-injector/hook.ts

@@ -1,5 +1,6 @@
 import type { PluginInput } from "@opencode-ai/plugin";
 import { createDynamicTruncator } from "../../shared/dynamic-truncator";
+import { resolveSessionEventID } from "../../shared/event-session-id";
 import { getRuleInjectionFilePath } from "./output-path";
 import { createSessionCacheStore, createSessionRuleScanCacheStore } from "./cache";
 import { createRuleInjectionProcessor } from "./injector";
@@ -80,16 +81,15 @@ export function createRulesInjectorHook(
     const props = event.properties as Record<string, unknown> | undefined;
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined;
-      if (sessionInfo?.id) {
-        clearSessionState(sessionInfo.id);
+      const sessionID = resolveSessionEventID(props);
+      if (sessionID) {
+        clearSessionState(sessionID);
       }
       clearProjectRootCache();
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID ??
-        (props?.info as { id?: string } | undefined)?.id) as string | undefined;
+      const sessionID = resolveSessionEventID(props);
       if (sessionID) {
         clearSessionState(sessionID);
       }