fed-sx-types Phase 6: DefineTrigger verb + trigger_registry

The trigger declaration layer (fed-sx-triggers-loop.md Phase 1): bind an
activity-type to a durable flow so an arriving activity can fan out into
a business flow.

- next/genesis/activity-types/define_trigger.sx — the DefineTrigger verb
  (DefineActivity form, nested-get schema). :object carries
  :activity-type, :flow-name, optional :guard / :actor-scope.
- next/kernel/trigger_registry.erl — pure core + registered gen_server,
  mirroring peer_actors/peer_types. Keyed by activity-type, multiple
  specs per type fire independently. Spec = {TriggerCid, FlowName,
  Guard, ActorScope}. Hydrates on start from a fold over DefineTrigger
  activities (restart-safe, same content-addressing as define_registry).

Manifest activity-types 7->8 (total bundle 38->39); the four bootstrap
count suites + genesis_parse bumped, and bootstrap_load's internal
timeout raised (the larger bundle's double cid:to_string was truncating).

Tests: define_trigger.sh (6), trigger_registry.sh (17). lib/erlang
771/771 + next/flow 34/34 untouched.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

next/genesis/activity-types/define_trigger.sx

@@ -0,0 +1,33 @@
+;; next/genesis/activity-types/define_trigger.sx
+;;
+;; Bootstrap definition of the DefineTrigger verb per
+;; plans/agent-briefings/fed-sx-triggers-loop.md (Phase 1) and
+;; plans/fed-sx-design.md §13. Read as data by the bundler
+;; (bootstrap.erl) — never evaluated as code.
+;;
+;; DefineTrigger binds an activity-type to a flow. When a matching
+;; activity is appended to the log, the kernel's trigger fan-out
+;; (pipeline.erl, post-append) looks the type up in the trigger
+;; registry and starts the named flow with the activity as input.
+;; The activity's :object is the binding record:
+;;   {:activity-type "Create"            ;; the verb to fire on
+;;    :flow-name     "blog-publish-digest"
+;;    :guard         <optional predicate> ;; discriminator
+;;    :actor-scope   <optional actor id>} ;; default: any
+;;
+;; The schema validates the *activity* shape: :object present with
+;; string :activity-type and :flow-name. The optional :guard lets one
+;; type bind to multiple flows with discriminators; it is resolved to
+;; an Erlang predicate at registration time (trigger_registry), not
+;; carried in the pure-predicate schema here. Schema bodies use nested
+;; `get` (not keyword-threading) so the predicate is evaluatable.
+(DefineActivity
+  :name "DefineTrigger"
+  :doc "Bind an activity-type to a flow. :object carries :activity-type, :flow-name, and optional :guard and :actor-scope."
+  :schema (fn
+    (act)
+    (and
+      (not (nil? (get act :object)))
+      (string? (get (get act :object) :activity-type))
+      (string? (get (get act :object) :flow-name))))
+  :semantics (fn (state act) state))

next/genesis/manifest.sx

@@ -24,7 +24,8 @@
     "activity-types/announce.sx"
     "activity-types/endorse.sx"
     "activity-types/define_type.sx"
-    "activity-types/subtype_of.sx")
+    "activity-types/subtype_of.sx"
+    "activity-types/define_trigger.sx")
   :object-types ("object-types/sx-artifact.sx"
     "object-types/note.sx"
     "object-types/tombstone.sx"