refactor: Use shared Cerebro Go API SDK

[jonathanhaaswriter]

Summary

Migrates Aperio's Cerebro integration to the shared Go SDK from writer/cerebro.

• Replaces the local Cerebro HTTP client implementation with a thin wrapper around github.com/writer/cerebro/sdk/go/cerebroapi.
• Reuses the shared Cerebro claim/URN helpers for claim construction.
• Keeps Aperio-specific defaults for runtime/source IDs and user agent.

Depends on: writer/cerebro#1139

Test Plan

• make test-go
• make lint

[github-actions]

Droid finished @jonathanhaaswriter's task —— View job

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I validated all candidate review comments and there were none to approve for posting. I did not identify a clear, high-confidence issue that warrants an inline review comment on this PR.

[github-actions]

Droid finished @jonathanhaaswriter's task —— View job

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The refactor cleanly replaces the local Cerebro HTTP implementation with the shared SDK and is well-structured overall. One data-integrity concern stands out: delegating EncodeExternalID to the SDK changes how spaces are encoded in URNs (from - to %20), which will silently orphan any Cerebro entities whose external IDs contained spaces, creating duplicates on re-ingestion. Additionally, the explicit HTTP redirect-blocking that guarded against SSRF via 3xx responses has been removed and should be confirmed present in the SDK.

[github-actions]

Droid finished @jonathanhaaswriter's task —— View job

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Validated all candidate review comments for PR #159. I did not approve any new inline comments. The current head preserves Aperio's external ID encoding behavior, and the shared Cerebro SDK retains redirect blocking, so I did not find a new high-confidence issue to post.

[github-actions]

Droid finished @jonathanhaaswriter's task —— View job

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Validated all candidates and approved none for posting. On the current head, Aperio still preserves its local external-ID URN encoding and the shared Cerebro SDK still blocks redirects, so I did not find a high-confidence inline issue to post.