fix(opencode): settle pending tool errors

[opencode-agent]

Summary

• settle tool errors even when the AI SDK emits tool-error before tool-call promotes the part from pending to running
• preserve the actual tool failure instead of replacing it with cleanup's Tool execution aborted marker
• add a deterministic processor regression covering the event ordering

Why

MCP isError results began rejecting in #32244. The AI SDK may publish the resulting tool-error while the tool part is still pending. failToolCall previously ignored that state and left its deferred unsettled, which can strand the provider turn.

Verification

• bun test test/session/processor-effect.test.ts (16 pass)
• bun typecheck in packages/opencode
• git diff --check

[github-actions]

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