fix(cursor): Pass prompt via stdin to avoid shell escaping issues

When passing file content (containing TypeScript code) to cursor-agent via
WSL, bash was interpreting shell metacharacters like $(), backticks, etc.
as command substitution, causing errors like "/bin/bash: typescript\r':
command not found".

Changes:
- subprocess.ts: Add stdinData option to SubprocessOptions interface
- subprocess.ts: Write stdinData to stdin when provided
- cursor-provider.ts: Extract prompt text separately and pass via stdin
- cursor-provider.ts: Use '-' as prompt arg to indicate reading from stdin

This ensures file content with code examples is passed safely without
shell interpretation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

libs/platform/src/subprocess.ts

@@ -12,6 +12,12 @@ export interface SubprocessOptions {
   env?: Record<string, string>;
   abortController?: AbortController;
   timeout?: number; // Milliseconds of no output before timeout
+  /**
+   * Data to write to stdin after process spawns.
+   * Use this for passing prompts/content that may contain shell metacharacters.
+   * Avoids shell interpretation issues when passing data as CLI arguments.
+   */
+  stdinData?: string;
 }
 
 export interface SubprocessResult {
@@ -24,22 +30,33 @@ export interface SubprocessResult {
  * Spawns a subprocess and streams JSONL output line-by-line
  */
 export async function* spawnJSONLProcess(options: SubprocessOptions): AsyncGenerator<unknown> {
-  const { command, args, cwd, env, abortController, timeout = 30000 } = options;
+  const { command, args, cwd, env, abortController, timeout = 30000, stdinData } = options;
 
   const processEnv = {
     ...process.env,
     ...env,
   };
 
-  console.log(`[SubprocessManager] Spawning: ${command} ${args.slice(0, -1).join(' ')}`);
+  // Log command without stdin data (which may be large/sensitive)
+  console.log(`[SubprocessManager] Spawning: ${command} ${args.join(' ')}`);
   console.log(`[SubprocessManager] Working directory: ${cwd}`);
+  if (stdinData) {
+    console.log(`[SubprocessManager] Passing ${stdinData.length} bytes via stdin`);
+  }
 
   const childProcess: ChildProcess = spawn(command, args, {
     cwd,
     env: processEnv,
-    stdio: ['ignore', 'pipe', 'pipe'],
+    // Use 'pipe' for stdin when we need to write data, otherwise 'ignore'
+    stdio: [stdinData ? 'pipe' : 'ignore', 'pipe', 'pipe'],
   });
 
+  // Write stdin data if provided
+  if (stdinData && childProcess.stdin) {
+    childProcess.stdin.write(stdinData);
+    childProcess.stdin.end();
+  }
+
   let stderrOutput = '';
   let lastOutputTime = Date.now();
   let timeoutHandle: NodeJS.Timeout | null = null;