A mid-stream connection drop showed a generic "Something went wrong / Load
failed" banner and left no server-side trace.
- error-message: classify the browsers' own fetch-failure strings ("Load
failed" on WebKit, "Failed to fetch" on Chrome, "NetworkError" on Firefox)
as a lost connection, so the banner names the cause instead of the generic
heading.
- ai-chat.controller: log a warning in the request close handler when the
client disconnects before completion, so a drop that reaches the app (e.g. a
reverse proxy cutting the SSE) is visible in the server logs before the abort.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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