fix(opencode): log silent auth and provider discovery errors

[MADEVAL]

Issue for this PR

Closes #34312

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Three catch blocks silently swallowed errors:

• auth/index.ts discarded invalid OPENCODE_AUTH_CONTENT JSON with no warning, falling through to file-based auth invisibly
• provider.ts GitLab model discovery returned {} on any failure with no indication the discovery itself failed
• the outer GitLab discovery caller had a second empty catch block

auth uses Effect.logWarning to surface the parse failure. provider's outer catch is replaced with Effect.catchAll + Effect.logWarning. provider's inner async discoverModels uses console.error since it is outside the Effect runtime.

How did you verify your code works?

Manual verification against repo logging patterns: auth follows the existing config.ts:548 pattern, provider follows workspace.ts:278.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

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