fed-sx-types Phase 1: DefineType + SubtypeOf genesis verbs

Two new DefineActivity-form genesis activity-types for host-type
federation (plans/fed-sx-host-types.md step 1):

- next/genesis/activity-types/define_type.sx — DefineType verb; schema
  accepts an :object with a string :name and optional list :fields.
- next/genesis/activity-types/subtype_of.sx — SubtypeOf verb; schema
  accepts an :object carrying string :child-type-cid + :parent-type-cid.

Schema bodies use nested `get` (not keyword-threading) so they are
directly evaluatable — keywords are not callable getters in the kernel.
Both registered in manifest.sx (activity-types now 7); the four bootstrap
suites' bundle counts bumped (5->7, total 36->38).

Tests: next/tests/define_type.sh (7), subtype_of.sh (6) — parse shape,
schema accept/reject, term_codec envelope round-trip.

Also load follower_graph + delivery in bootstrap_start.sh: its check-26
publish path exercises outbox:compute_delivery_set/3 (follower_graph:new
+ delivery:delivery_set), which an m2 substrate change had left unloaded
in that suite — a pre-existing red unrelated to the count bump.

Conformance 771/771; all touched next/tests green.

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

next/tests/bootstrap_start.sh

@@ -54,6 +54,12 @@ cat > "$TMPFILE" <<EPOCHS
 (eval "(get (erlang-load-module (file-read \"next/kernel/nx_kernel.erl\")) :name)")
 (epoch 10)
 (eval "(get (erlang-load-module (file-read \"next/kernel/bootstrap.erl\")) :name)")
+;; outbox:publish computes a delivery set via follower_graph + delivery
+;; (compute_delivery_set/3) — load both so the publish path resolves.
+(epoch 11)
+(eval "(get (erlang-load-module (file-read \"next/kernel/follower_graph.erl\")) :name)")
+(epoch 12)
+(eval "(get (erlang-load-module (file-read \"next/kernel/delivery.erl\")) :name)")
 
 ;; bootstrap:start returns a Pid
 (epoch 20)
@@ -115,10 +121,10 @@ check() {
 
 check 10  "bootstrap module loaded"           "bootstrap"
 check 20  "whereis(nx_kernel) is Pid"         "true"
-check 21  "activity_types count = 5"          "5"
+check 21  "activity_types count = 7"          "7"
 check 22  "object_types count = 13"           "13"
 check 23  "projections count = 7"             "7"
-check 24  "total entries = 36"                "36"
+check 24  "total entries = 38"                "38"
 check 25  "fresh log_tip = 0"                 "0"
 check 26  "publish advances tip to 1"         "1"
 check 27  "actor_id = alice"                  "true"