v0.13.0

New features:

• LogEntry::is_truncated(&Field) answers whether the logger's write buffer cut
  short the text a field span covers, so a consumer rewriting spans can withhold
  a partial value instead of scrubbing it blind. LogEntry::cut_texts names the
  entry's texts that ended at a cut.
• Every slot of a CHANNEL_DATA dump now carries a span for its value. A name
  outside the identity vocabulary spans as FieldKind::VariableValue, so an
  identity-carrying slot the mapping does not name no longer reaches a consumer
  unlocated; the consumer decides sensitivity from the name.
• The value a dialplan Regex condition tested is spanned, and RegexCondition
  with the slicer that cuts it is public API.
• Three core narrations that never classified as a channel variable now do:
  EXPORTING, "setting variable", and set()'s PUSH/UNSHIFT verbs.

Bug fixes:

• An SDP body whose marker sits on a continuation line becomes a Block::Sdp
  rather than untyped text — the shape sofia logs for outbound invites, and the
  majority of Local SDP occurrences in production logs. A body carrying no
  marker opens on its version line.
• A CHANNEL_DATA value the logger cut no longer swallows the variable that
  follows it on the collided line; the value closes at the cut with a
  TruncatedVariable warning.
• A bracketed value ends at its matching bracket rather than the first one, so a
  value containing brackets is no longer cut short. SET GLOBAL no longer yields
  a channel span.

Breaking:

• LogEntry gained the cut_texts field, so literal construction needs updating.
  LogEntry::synthetic plus struct-update syntax keeps compiling.