Document whitespace trimming in operation-label normalization

Co-authored-by: Shri Sukhani <shrisukhani@users.noreply.github.com>

Author: cursoragent

README.md

@@ -155,7 +155,7 @@ Polling callback contracts are also validated:
 - Async loop contract runtime errors (e.g. `Future attached to a different loop`, `Task is bound to a different event loop`, `Non-thread-safe operation invoked on an event loop other than the current one`, `Event loop is closed`) are treated as non-retryable and surfaced immediately.
 - Executor-shutdown runtime errors (e.g. `cannot schedule new futures after shutdown`) are treated as non-retryable and surfaced immediately.
 - Wait helpers (`start_and_wait`, `wait_for_job_result`) only execute fetch/result callbacks after terminal status is reached; polling failures/timeouts short-circuit before fetch retries begin.
-- SDK-managed job operation labels derived from job IDs are automatically normalized and bounded (control-character cleanup + truncation) to satisfy polling operation-name validation limits.
+- SDK-managed job operation labels derived from job IDs are automatically normalized and bounded (whitespace trimming, control-character cleanup, and truncation) to satisfy polling operation-name validation limits.
 
 Example: