refactor: restructure PrismFacet per OpenClaw plugin spec

- plugin/ directory structure: hooks/, tools/, core/
- export default { id, name, register } entry format
- globalThis state management with lifecycle protection
- WeakSet dedup on before_prompt_build hook
- Tool uses inputSchema + execute (not parameters + handler)
- additionalProperties: false in config schema
- Core logic in plugin/core/ (no plugin-sdk dependency)
- Install/uninstall script (scripts/install.mjs)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plugin/core/router-loader.ts

@@ -0,0 +1,77 @@
+import { readdirSync } from "node:fs";
+import path from "node:path";
+
+export interface RouterContext {
+  agentId: string;
+}
+
+export interface RouterModule {
+  resolve(ctx: RouterContext): string | Promise<string>;
+}
+
+export interface LoadedRouter {
+  name: string;
+  filePath: string;
+  module: RouterModule;
+}
+
+const _G = globalThis as Record<string, unknown>;
+const ROUTERS_KEY = "_prismFacetRouters";
+const LOAD_COUNTER_KEY = "_prismFacetLoadCounter";
+
+function getRouterMap(): Map<string, LoadedRouter> {
+  if (!(_G[ROUTERS_KEY] instanceof Map)) {
+    _G[ROUTERS_KEY] = new Map<string, LoadedRouter>();
+  }
+  return _G[ROUTERS_KEY] as Map<string, LoadedRouter>;
+}
+
+function routerNameFromFile(filename: string): string {
+  return filename.replace(/\.(ts|js|mjs)$/, "");
+}
+
+export async function loadRouters(
+  routersDir: string,
+  log: { info(msg: string): void; warn(msg: string): void }
+): Promise<void> {
+  const map = getRouterMap();
+  map.clear();
+
+  if (typeof _G[LOAD_COUNTER_KEY] !== "number") _G[LOAD_COUNTER_KEY] = 0;
+  (_G[LOAD_COUNTER_KEY] as number)++;
+  const counter = _G[LOAD_COUNTER_KEY] as number;
+
+  let files: string[];
+  try {
+    files = readdirSync(routersDir).filter(
+      (f) => /\.(ts|js|mjs)$/.test(f) && !f.startsWith(".")
+    );
+  } catch {
+    log.warn(`[prism-facet] routers directory not found: ${routersDir}`);
+    return;
+  }
+
+  for (const file of files) {
+    const name = routerNameFromFile(file);
+    const filePath = path.resolve(routersDir, file);
+    try {
+      const mod = (await import(`${filePath}?v=${counter}`)) as RouterModule;
+      if (typeof mod.resolve !== "function") {
+        log.warn(`[prism-facet] router ${name}: no resolve() export, skipping`);
+        continue;
+      }
+      map.set(name, { name, filePath, module: mod });
+      log.info(`[prism-facet] router loaded: ${name}`);
+    } catch (err) {
+      log.warn(`[prism-facet] router ${name}: failed to load — ${String(err)}`);
+    }
+  }
+}
+
+export function getRouters(): LoadedRouter[] {
+  return Array.from(getRouterMap().values());
+}
+
+export function getRouterNames(): string[] {
+  return Array.from(getRouterMap().keys());
+}