slog-configurator v1.3.0 — searchable log ring

logring can now be searched by structured attribute, not just by substring of
the formatted line. Attributes are captured from the slog.Record when it is
handled rather than parsed back out, so field search behaves identically in
text mode and in JSON, and it picks up attributes bound earlier through
slog.Logger.With -- which live on the inner handler and never appear on the
record. Grouped attributes flatten to dotted keys.

SearchOptions also gains Exclude, Match (regexp), Until, Levels, Offset and
Ascending; Count, Tail and Clear join Search and Stats.

Three fixes: a record larger than MaxBytes used to be admitted and then evict
the entire ring, counting as neither stored nor dropped -- MaxRecordBytes is
now clamped to MaxBytes so it is refused up front. The stored line no longer
carries the trailing newline it never needed. The byte budget now counts
everything an entry retains, not only the formatted line.