- logging: pre-allocate fresh slice for request field to avoid mutating
fasthttp internal buffers via append into slices with excess capacity
- mimeutil: move defaultMIME fallback before cache insertion so unknown
extensions are consistently cached as application/octet-stream
- builtin: use -0700 timezone format instead of hardcoded +0800; cache
generated request_id in UserValue to prevent different IDs per expansion
- variable: initialize maps in fallback Context to prevent nil map panic