fix: resolve SDK spawn failures and sharp native binary crashes

- Strip CLAUDECODE env var from SDK subprocesses to prevent "cannot be
  launched inside another Claude Code session" error (Claude Code 2.1.42+)
- Lazy-load @chroma-core/default-embed to avoid eagerly pulling in
  sharp native binaries at bundle startup (fixes ERR_DLOPEN_FAILED)
- Add stderr capture to SDK spawn for diagnosing future process failures
- Exclude lockfiles from marketplace rsync and delete stale lockfiles
  before npm install to prevent native dep version mismatches

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/shared/EnvManager.ts

@@ -27,6 +27,7 @@ export const ENV_FILE_PATH = join(DATA_DIR, '.env');
 // are passed through to avoid breaking CLI authentication, proxies, and platform features.
 const BLOCKED_ENV_VARS = [
   'ANTHROPIC_API_KEY',  // Issue #733: Prevent auto-discovery from project .env files
+  'CLAUDECODE',         // Prevent "cannot be launched inside another Claude Code session" error
 ];
 
 // Credential keys that claude-mem manages