chore(node-sdk): audit providers claudecode codex cursor gemini

Add plugins/shell-command.ts for the shared quoting and command parsers; runtime status checks go through managed-runtime-status; Codex and Cursor write through managed-transaction.

Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq

src/plugins/claudecode-contract.ts

@@ -1,5 +1,6 @@
 import os from 'node:os';
 import path from 'node:path';
+import { sameAgentId, samePath } from './common.js';
 import { isObject, parseStrictJsonObject, type JsonObject } from './strict-json.js';
 
 export const AGENT_KEY = 'claudecode';
@@ -76,20 +77,6 @@ interface RuntimeReference {
   readonly scriptPath: string;
 }
 
-function samePath(left: string, right: string): boolean {
-  const normalizedLeft = path.resolve(left);
-  const normalizedRight = path.resolve(right);
-  return process.platform === 'win32'
-    ? normalizedLeft.toLowerCase() === normalizedRight.toLowerCase()
-    : normalizedLeft === normalizedRight;
-}
-
-function sameAgentId(left: string, right: string): boolean {
-  return process.platform === 'win32'
-    ? left.toLowerCase() === right.toLowerCase()
-    : left === right;
-}
-
 function requireKnownKeys(value: JsonObject, allowed: readonly string[], label: string): void {
   const keys = new Set(allowed);
   const extra = Object.keys(value).find((key) => !keys.has(key));