[许钊瑞 (xuzhaorui)]

Summary

Clarifies the concurrency semantics of Sequenced.remainingCapacity() in response to #511.

The method does not provide an atomic capacity snapshot. Under concurrent producers, sequences may be reserved before they are published, and the estimate may be stale or negative while producers contend for a full buffer. The documentation now recommends hasAvailableCapacity(int) or tryNext() when a capacity decision must be correct.

This intentionally does not change the existing cursor-read order: as discussed in #511, reading the cursor once or twice has different consistency trade-offs, and neither option is universally preferable.

Validation

• git diff --check passed.
• Gradle tests could not be run locally because the Gradle 8.10 wrapper distribution download timed out in the environment.
• No runtime behavior was changed; this is a Javadoc-only change.

Closes #511