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/tests/bootstrap_load.sh

@@ -79,7 +79,7 @@ cat > "$TMPFILE" <<'EPOCHS'
 (eval "(get (erlang-eval-ast \"R = bootstrap:read_genesis(), {ok, S1} = bootstrap:load_genesis(R), {ok, S2} = bootstrap:load_genesis(R), cid:to_string(S1) =:= cid:to_string(S2)\") :name)")
 EPOCHS
 
-OUTPUT=$(timeout 300 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
+OUTPUT=$(timeout 590 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
 
 check() {
   local epoch="$1" desc="$2" expected="$3"
@@ -106,7 +106,7 @@ check 10  "strip suffix create.sx -> create"    "true"
 check 11  "strip suffix hello unchanged"        "true"
 check 12  "strip suffix .sx -> empty"           "true"
 check 13  "load_genesis rejects bad shape"      "ok"
-check 20  "loaded activity_types count = 7"     "7"
+check 20  "loaded activity_types count = 8"     "8"
 check 21  "loaded object_types count = 13"      "13"
 check 22  "loaded projections count = 7"        "7"
 check 23  "loaded validators count = 3"         "3"