[GITHUBTANMAY2003]

Description

S3 Vectors errors currently reach users as low-level Botocore ClientError exceptions. This PR translates the common not-found, access-denied, and validation failures into dynavec exceptions that are easier for applications to handle.

Related issue

Fixes #15

Changes

• Added AccessDeniedError and ValidationError, alongside the existing NotFoundError.
• Added a shared error translator used by both the synchronous and asynchronous S3 Vectors stores.
• Covered direct requests, paginated operations, and concurrent uploads.
• Kept unknown and temporary AWS errors unchanged so the existing retry logic continues to work.
• Added offline tests for error mapping, retries, pagination, and concurrent failures.

Testing

• 107 affected tests passed, including 56 new error-handling tests
• Ruff passed
• Mypy passed
• Full suite passed locally with the OpenAI import-order workaround
• Documentation update not required.

[Kaap10]

LGTM. The error translation helper maps S3 Vectors client errors cleanly across sync, async, and paginated operations while preserving retry behavior for transient errors. Verified locally with all 56 new tests and full suite passing.