[TheGreatAxios]

Summary

• Drops the no-op connectListProviders export (it returned FIRST_CLASS_PROVIDERS unchanged) and its test; no host re-exports it.
• buildGoCatalogEntry builds its protocol map from the shared PROTOCOL_BY_ID instead of re-iterating the model array.
• formatGoUsage formats via named helpers (formatUsagePercent, usageWindowLabel) instead of nested ternaries.
• Go and Zen identity share one hostMatchesOpencodeDotAi helper (homed in opencode-go, imported by zen) with the same boolean outcome at each site.

Verification

• Item 1: connectListProviders referenced only by providers.test.ts; not re-exported in index.ts — deleted export and test.
• Item 2: PROTOCOL_BY_ID derives from the same OPENCODE_GO_MODELS ids/protocols as the replaced loop; Object.fromEntries(PROTOCOL_BY_ID) yields an identical map.
• Item 3: extracted helpers preserve the exact formatting branches (pct percent / dollars / "ok"; window 5h / week / month).
• Item 4: isOpenCodeGoURL and isZenURL keep identical host-match outcomes — Go inverts the shared helper.
• bun test packages/opencode-go/src packages/zen/src packages/first-class-providers/src — 57 pass, 0 fail.
• bun run typecheck — passes.
• oxlint and oxfmt --check on changed files — clean.

Fixes CL-10530

[linear-code]

CL-10530

[corbits-triage]

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