Optional OTLP export of request-level metrics (request and response-byte
counters keyed by route/status/conditional-GET, a duration histogram out
to 600s) plus server spans for slow or 5xx requests, nested under the
incoming W3C trace context. Off unless an OTLP endpoint or uptrace DSN is
configured; a config-less server is byte-for-byte unchanged.
Thin local front-end over ANW-26's merge engine (query::execute_merge):
walk the vault once (vault::scan, same as doctor), evaluate the --query
string, assemble the merged document, write it to stdout. No HTTP, no
watcher, no index. Byte-identical to the HTTP merge mode for the same
vault and query.
