fix: align error handling with OpenCode plugin conventions (#80)

[CasualDeveloper]

Summary

• Token refresh failures now throw errors instead of returning Response objects
• API error responses returned as-is for OpenCode/AI SDK to handle properly
• Matches the pattern used by opencode-copilot-auth and opencode-anthropic-auth

Problem

The plugin's error handling didn't follow OpenCode plugin conventions, causing errors to display incorrectly in the UI (persisting errors, raw JSON output).

Changes

lib/request/fetch-helpers.ts

• refreshAndUpdateToken(): Now throws Error on failure instead of returning { success: false, response }
• handleErrorResponse(): Returns original response as-is (clones for logging) instead of consuming and enriching it

index.ts

• Simplified token refresh call - errors propagate naturally via throw

test/fetch-helpers.test.ts

• Updated test to match new behavior

Result

Errors now display correctly in the UI:

References

• Pattern from opencode-copilot-auth: https://github.com/sst/opencode/blob/main/packages/opencode/src/session/message-v2.ts
• Fixes [BUG] Error handling pattern doesn't match OpenCode plugin conventions (#81) #80

[Copilot]

Pull request overview

This PR refactors error handling to align with OpenCode plugin conventions, ensuring errors are properly displayed in the UI. The key changes involve making token refresh failures throw errors instead of returning Response objects, and returning API error responses as-is for the OpenCode/AI SDK to handle.

Key Changes

• Token refresh failures now throw Error instead of returning { success: false, response } objects
• API error responses are returned unchanged (using response.clone() for logging) instead of enriching them with additional fields
• Simplified error handling in the main fetch function by letting errors propagate naturally

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
lib/request/fetch-helpers.ts	Updated refreshAndUpdateToken() to throw on failure; modified handleErrorResponse() to return original response using clone; removed unused HTTP_STATUS import and toNumber() helper
index.ts	Simplified token refresh call by removing error check logic (errors propagate via throw)
test/fetch-helpers.test.ts	Updated test to verify original response is preserved instead of checking for enriched error fields

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[CasualDeveloper]

Added tests for refreshAndUpdateToken() in the follow-up commit (e80e7b2) to address the Copilot review feedback.

The tests cover:

• Error path: verifies the function throws when refreshAccessToken() returns { type: 'failed' }
• Success path: verifies auth state is updated and client.auth.set() is called with correct parameters

[CasualDeveloper]

Accidentally closed it when I just wanted to rename it. Reopened.