fix: emit tool-input-end eagerly for sequential tool calls

[threepointone]

Summary

Fixes #488.

• Emit tool-input-end + tool-call eagerly when a new tool call index starts streaming, instead of batching all of them at stream close in flush(). This matches the behavior of other AI SDK providers like @ai-sdk/openai-compatible.
• Use the null finalization chunk as an explicit close signal. Previously this sentinel was detected and discarded; now it triggers tool-input-end for the active tool call.
• Guard against double-close via a closedToolCalls set — if both a finalization chunk and a new-index-start would close the same tool, only the first one emits events.

Before

All tool-input-end events emitted simultaneously at stream close:

tool-input-start(0) → deltas → tool-input-start(1) → deltas → [stream ends] → tool-input-end(0), tool-call(0), tool-input-end(1), tool-call(1)

After

Each tool call is closed before the next one starts:

tool-input-start(0) → deltas → tool-input-end(0) → tool-call(0) → tool-input-start(1) → deltas → tool-input-end(1) → tool-call(1)

Test plan

• 11 new tests covering: sequential tool calls (2 and 3 tools), null finalization chunks, double-close prevention, batch tool calls in a single SSE event, OpenAI format, text + tool call interleaving, single tool call (regression)
• All 236 existing unit tests pass with no modifications

Made with Cursor

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Latest commit: ed6112a

The changes in this PR will be included in the next version bump.

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workers-ai-provider	Patch

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