Improve behavior authoring and typed trace history (untested checkpoint)

docs/language.rst

@@ -103,6 +103,9 @@ lists all additional fields. ``ref`` means ``@alias``; ``ref?`` also accepts
    * - ``oa_exchange_item``, ``sa_exchange_item``
      - ``kind``: Information, Material, Energy; ``mechanism``: ExchangeMechanism; ``supertype``: item ref?
      - Information; Unspecified; none
+   * - ``oa_exchange_category``, ``sa_exchange_category``
+     - ``family``: Work or Participant; ``exchanges``: same-layer exchange refs
+     - Work; ``[]``; root-level only
    * - ``oa_data_type``, ``sa_data_type``
      - ``definition``: DataTypeDefinition; ``default``: DataValue?; ``unit``: string
      - String with minimum_length 0 / maximum_length none; none; ``""``
@@ -223,7 +226,9 @@ The present Studio profile does not decompose SA Actors.
 
 All relations have a header identity, alias, display name, optional
 ``description`` (default ``""``), and required ``source`` and ``target``
-references. Their kind is the declaration keyword:
+endpoints. Ordinary endpoints are semantic references; ContextualLink endpoints
+are qualified OccurrenceEndpoint records resolved from its required ``owner``.
+Their kind is the declaration keyword:
 
 .. list-table:: Relation catalog
    :header-rows: 1
@@ -286,6 +291,9 @@ references. Their kind is the declaration keyword:
    * - ``sequence_link``
      - Preceding contribution → following contribution in one process/chain
      - ``guard`` string / ""
+   * - ``contextual_link``
+     - Qualified occurrence endpoints resolved from an explicit owner Process/FunctionalChain; section 4.2.1
+     - Required ``owner``, ``source`` and ``target`` OccurrenceEndpoint records, and typed ``purpose``: Precedence, Exchange or CommonWork
    * - ``state_transition``
      - State vertices in one machine, subject to section 4.4
      - ``trigger``, ``guard``, ``effect`` strings / ""; ``transition_kind`` External; ``triggers``, ``effects`` reference lists / []
@@ -1190,7 +1198,7 @@ are invalid.
    * - Mission
      - Operational Mission → System Mission
    * - Exchange
-     - Interaction relation → FunctionalExchange relation
+     - Interaction → FunctionalExchange, or CommunicationMean → BoundaryExchange
    * - Sequence
      - Process → FunctionalChain, or paired occurrence contributions directly owned by Process / FunctionalChain
    * - Item