fix(translation): don't terminate stream on per-batch JSON parse failures

[Copilot]

A failed JSON parse in any batch (e.g. "Failed to parse translation response for batch 9") emitted a terminal error event, closing the SSE stream. The worker kept running, but every client reconnect replayed the cached events and re-closed at the same error — surfacing as the same error replaying forever with the run never completing.

Changes

• lib/translation/xcloc/events.ts: Add non-terminal batch-error event ({ batchIndex, message }), parallel to the existing save-error.
• lib/translation/xcloc/agent.ts: translateBatch yields batch-error instead of error on parse failure, and falls through to the existing batch-complete so the worker saves progress and continues to subsequent batches / final complete.
• lib/translation/components/use-translation-stream.ts: Handle batch-error like save-error — append to the errors list, keep the stream open.
• __tests__/translation/xcloc/agent.test.ts: Update the invalid-JSON test to assert batch-error (the run still ends with complete).

error remains terminal and reserved for actual run-fatal failures (raised by the worker's outer retry loop).

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Project	Deployment	Actions	Updated (UTC)
universal-translation	Ready	Preview, Comment	Apr 24, 2026 11:01am

[Copilot]

Pull request overview

This PR prevents per-batch JSON parse failures during Xcloc translation runs from terminating the SSE stream by introducing a non-terminal batch-error event, allowing the worker to continue processing subsequent batches and reach complete.

Changes:

• Added a new batch-error event type for non-fatal, per-batch failures.
• Updated translateBatch to emit batch-error (and still emit batch-complete) when parsing fails, instead of emitting terminal error.
• Updated the stream consumer hook and the corresponding agent test to handle/assert batch-error.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
lib/translation/xcloc/events.ts	Extends the Xcloc event union with non-terminal batch-error.
lib/translation/xcloc/agent.ts	Emits batch-error on per-batch parse failures and proceeds to batch-complete.
lib/translation/components/use-translation-stream.ts	Treats batch-error as non-terminal by appending to errors without closing the stream.
tests/translation/xcloc/agent.test.ts	Updates invalid-JSON coverage to assert batch-error while still completing.

[sirily11]

🎉 This PR is included in version 1.2.2 🎉

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