fed-sx-m2: Step 2a — Person/Service/Group genesis object-types

Three new DefineObject artefacts in next/genesis/object-types/ for
the canonical actor object-types per design §9.1:

- Person: human-controlled identity (display name + handle + bio)
- Service: automated / programmatic actor (bot, feed, organisation)
- Group: multi-controller actor (member-set managed via Add/Remove)

Each is a small SX form with :name / :doc / :schema, identical
shape to existing object-types (note.sx, sx-artifact.sx etc) so the
existing bootstrap:populate_registry walk picks them up without
code changes. Manifest extended (object-types: 10 -> 13, total
entries: 31 -> 34).

Tests:
- genesis_parse.sh +7 cases (head form, :name, manifest membership);
  57/57.
- Hardcoded counts bumped in bootstrap_read.sh, bootstrap_load.sh,
  bootstrap_populate.sh, bootstrap_start.sh.
- bootstrap_build.sh 12/12 (bundle CID computed dynamically).

Conformance 761/761 preserved. 211/211 across 12 Step-2-adjacent
suites.

next/tests/bootstrap_read.sh

@@ -103,7 +103,7 @@ check 11  "ends_with_sx create.sx"          "true"
 check 12  "ends_with_sx hello"              "false"
 check 13  "ends_with_sx empty"              "false"
 check 20  "section activity_types count"    "3"
-check 21  "section object_types count"      "10"
+check 21  "section object_types count"      "13"
 check 22  "section projections count"       "7"
 check 23  "section validators count"        "3"
 check 24  "section codecs count"            "3"