[Xuanwo]

Which issue does this PR close?

Related to #7577.

Rationale for this change

Two HF dataset behavior-test attempts on 26f2b5cf exhausted the 10-second I/O deadline while writing test fixtures. Temporary dataset cleanup also returned 404 because the deletion request passed the full repository ID as its bare name.

What changes are included in this PR?

• Allow a positive whole-second OPENDAL_TEST_IO_TIMEOUT in the behavior testkit and use 30 seconds for the HF dataset fixture. Reset the override between fixtures using the existing environment sentinel.
• Send the namespace and bare repository name separately when deleting temporary datasets. Keep bucket deletion on its existing endpoint.
• Run regression tests through the actual cleanup entry point in Check CI.

Validation on nier covered the cleanup entry point, testkit lint/format checks, and real Memory behavior with the override, reset sentinel, invalid value, and zero value. The HF diagnostic run passed 109 dataset, 109 bucket, and 109 bucket-HTTP tests, followed by three successful cleanup DELETE requests. The runtime files match this PR's 4c5d89b7; the diagnostic workflow selector and runner are excluded from the PR. Full PR CI will run on publication.

Are there any user-facing changes?

Behavior-test configuration gains an optional I/O timeout. Production timeout defaults and retry counts stay unchanged.

Breaking changes

AI Usage Statement

• Harness: Codex. Model: GPT-6 family; exact runtime identifier unavailable to this task. Effort: unavailable to this task. Role: implementation, coordination, and validation.
• Harness: Codex subagent. Model: group/deepseek. Effort: max. Role: independent review and validation on nier.