fix: map empty content errors to 429 for client retry

fix: try extension port as LS fallback, increase cache TTL to 5min, invalidate on failure

fix: robust error handling, discovery, and SSE stream reliability

feat: multi-provider API support and sidecar stability fixes

fix(stability): format long logs to file and emit keep-alive SSE chunks

feat(debug): add opt-in logToFile configuration setting

fix(stream): ensure role property is set on first tool_call-only chunk

feat: handle native Claude 3 tool use schemas

feat: wrap tool results in observation tags to align with XML model schemas

fix(sse): reduce stream initialization delay to 2s to prevent client TTFB timeouts

feat: parse native XML tool usage for Minimax and Claude models

feat: rip out legacy fallbacks to strictly enforce raw inference; fix: defer SSE headers to allow pure HTTP 429 backoff signals

fix: correctly interpret upstream HTTP 500/503 internal errors and short-circuit cascade fallback

fix: send Retry-After headers and native APIError objects for streaming capacity errors

fix: increase raw inference timeout to 15m for large context operations