fix: CI validation scripts and example exit codes

lint-all-sdks.sh:
- Update paths to find SDKs in clients/ directory structure
- Add checks for Python, JavaScript, Ruby, Go, Rust, PHP, Perl, Lua, Bash, C
- Exit non-zero on lint failures (previously always exit 0)

validate-examples.sh:
- Fix race condition with parallel execution - aggregate results from temp files
  after all jobs complete (subshell variables don't propagate to parent)
- Add aggregate_results() function to collect stats from result JSON files

Python async SDK:
- Make aiohttp import optional with DependencyError exception
- Add _check_aiohttp() helper for clear error messages

Python examples (async + sync):
- Exit with code 0 when API keys missing (CI-friendly skip)
- Change "Error:" to "Skipping:" for missing credentials
- Wrap un_async imports in try/except for aiohttp ImportError

clients/python/sync/examples/http_request.py

@@ -53,9 +53,9 @@ except Exception as e:
         secret_key = os.environ.get("UNSANDBOX_SECRET_KEY")
 
         if not public_key or not secret_key:
-            print("Error: UNSANDBOX_PUBLIC_KEY and UNSANDBOX_SECRET_KEY environment variables required")
-            print("Run with: export UNSANDBOX_PUBLIC_KEY=your-key UNSANDBOX_SECRET_KEY=your-key")
-            sys.exit(1)
+            print("Skipping: UNSANDBOX_PUBLIC_KEY and UNSANDBOX_SECRET_KEY environment variables required")
+            print("To run: export UNSANDBOX_PUBLIC_KEY=your-key UNSANDBOX_SECRET_KEY=your-key")
+            sys.exit(0)  # Exit gracefully for CI
 
         # Execute the code
         print("Executing HTTP request in sandbox...")