fix(block): classify block I/O errors into retryable and fatal

[emersonbusson]

Summary

Classify block I/O errors into retryable and fatal categories by defining IoError as an enum and mapping IoError::Retryable to NBD_ENOSPC

Commits

Commit	Files	Validation	Risk/rollback
dbd9079	protocol.rs, request.rs, downstream files	Ran cargo test, Validated red tests	Client unexpected retry loops on transient failure

Issue

fix(block): classify block I/O errors into retryable and fatal

Owner

ResilienceChaos100

Labels

type: fix
area: block

Validation

Passed all tests including red_test.

Rollback trigger

Client unexpected retry loops on transient failure

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PR created automatically by Jules for task 4392579080887799761 started by @emersonbusson

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[emersonbusson]

Closed in favor of PR #2085 consolidation.

[google-labs-jules]

Closed in favor of PR #2085 consolidation.

Understood. Acknowledging that this work is now obsolete and stopping work on this task.