fix(cross-plugin-api): drain __prismFacetPending queue from early consumers

Plugin load order is undefined. If a consumer (ClawPrompts) loads
before PrismFacet, it can't call __prismFacet.addRouter directly
(slot is undefined). Now it pushes ops onto the well-known
__prismFacetPending array; PrismFacet's installCrossPluginApi()
drains the queue when it runs. Marker __real: true on the installed
API so consumers can tell stub from real.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plugin/core/cross-plugin-api.ts

@@ -48,22 +48,34 @@ export interface PrismFacetCrossPluginApi {
   ): void;
 }
 
-/** Idempotent install. Called from PrismFacet's register(). Also runs
+type PendingOp =
- * at module-import time below so that consumer plugins loading before
+  | { type: "router"; name: string; resolve: (ctx: RouterContext) => string | Promise<string> }
- * PrismFacet still find a usable API. */
+  | { type: "rule"; routerName: string; key: string; prompt: { file?: string; text?: string } };
+
+/**
+ * Idempotent install. Called from PrismFacet's register(). Also runs
+ * at module-import time below so consumer plugins loading before
+ * PrismFacet still find a usable API.
+ *
+ * Plugin load order is undefined — if ClawPrompts loads before
+ * PrismFacet, the `_G['__prismFacet']` slot stays at the buffering stub
+ * created by ClawPrompts (or, if neither has installed yet, missing).
+ * To make this race-free, we install the real API on first call from
+ * either side AND drain any queued ops a buffering caller may have
+ * accumulated via the well-known `__prismFacetPending` array. ClawPrompts
+ * (and any future consumer) only needs to: push ops onto the pending
+ * array when `__prismFacet?.addRouter` isn't callable; PrismFacet's
+ * install() will drain them when it runs.
+ */
 export function installCrossPluginApi(): PrismFacetCrossPluginApi {
   const existing = _G["__prismFacet"] as PrismFacetCrossPluginApi | undefined;
-  if (existing && typeof existing.addRouter === "function") return existing;
+  if (existing && typeof existing.addRouter === "function" && (existing as any).__real) return existing;
 
-  const api: PrismFacetCrossPluginApi = {
+  const api: PrismFacetCrossPluginApi & { __real: true } = {
     addRouter(name, resolve) {
       addExternalRouter(name, resolve);
     },
     addRule(routerName, key, prompt) {
-      // Phase 1: only file-based prompts are wired through the existing
-      // injector. `text` inline prompts will need a tmpfile-or-store
-      // backend; surfaced as a TODO so an early caller failing loudly
-      // beats silently dropping the prompt.
       if (!prompt.file) {
         throw new Error(
           "__prismFacet.addRule: only { file: '/abs/path.md' } is supported today; " +
@@ -72,12 +84,27 @@ export function installCrossPluginApi(): PrismFacetCrossPluginApi {
       }
       addExternalRule(routerName, key, prompt.file);
     },
+    __real: true,
   };
   _G["__prismFacet"] = api;
+
+  // Drain any ops queued by consumer plugins that ran before us.
+  const pending = _G["__prismFacetPending"] as PendingOp[] | undefined;
+  if (Array.isArray(pending) && pending.length > 0) {
+    for (const op of pending) {
+      try {
+        if (op.type === "router") api.addRouter(op.name, op.resolve);
+        else api.addRule(op.routerName, op.key, op.prompt);
+      } catch {
+        // Swallow per-op errors so one bad pending entry doesn't block
+        // the rest. Consumer plugin logs already fired at queue time.
+      }
+    }
+    _G["__prismFacetPending"] = [];
+  }
+
   return api;
 }
 
-// Eager install on module load so a consumer plugin importing into the
+// Eager install on module load.
-// same gateway process can register even if it runs before PrismFacet's
-// register() does.
 installCrossPluginApi();