[klezaic]

Summary

• Reject invalid stream names up front in JetStreamContext::createStream and
  updateStream with a clear \InvalidArgumentException naming the offending
  value, instead of letting the request time out waiting for a reply that will
  never come.
• Rules mirror NATS server validation: non-empty, and no whitespace, ., *,
  >, /, \, or control characters.
• createOrUpdateStream picks up the guard transitively.

Why

A bad character in the stream name produced
Sofascore\Nats\TimeoutException: Subscription nextMessage timed out, which
gave no signal that the caller's input was the problem. Fixing this at the
boundary turns a hard-to-diagnose timeout into an actionable error.

Fixes #81

Test plan

• vendor/bin/phpunit --testsuite=unit passes (includes the new
  JetStreamContextStreamNameValidationTest covering each forbidden char
  class plus empty input and 6 valid shapes).
• vendor/bin/phpstan analyse --no-progress clean.
• vendor/bin/php-cs-fixer fix --dry-run --diff clean.
• Manual: calling createStream(new StreamConfig(name: 'bad.name')) now
  throws \InvalidArgumentException immediately instead of timing out.