host: metamodel create-relation form (session-scoped) + keep load-rel-kinds! unrolled

Define a relation through the UI (metamodel editor surface 1, completing it):
POST /meta/new-relation creates a relation-post (is-a relation, :rel metadata) and
registers it via a runtime concat onto host/blog-rel-kinds — safe because the serving
handler has the IO resolver installed. /meta gains a '+ Relation' form (name, label,
symmetric). Verified: define 'Blocks' (symmetric) -> Relations(5), its editor renders on
edit pages, kind-spec + symmetric correct; auth-guarded.

SESSION-SCOPED: the relation-post + edges persist durably, but the rel-kinds registry
entry is lost on restart because load-rel-kinds! must stay UNROLLED — it runs at BOOT
where it is JIT-compiled but the IO resolver is NOT yet installed, so a dynamic loader
(map/reduce over instances-of 'relation' with a durable read per item) silently returns []
(verified: dynamic -> /meta Relations(0)). The serving-JIT HO-callback-perform fix only
engages with the resolver = serve time. Flagged to sx-vm-extensions (NOTE-render-diff-for-
vm-ext.md); they ACKed + are tracking the boot-resolver fix. Reverted the dynamic loader,
kept the unroll with a comment explaining why.

VERIFICATION NOTE: the full blog suite could not complete — the box is under extreme
contention from sibling loops (load 14, multiple full conformance + erlang/vm-ext rebuilds)
and the Datalog-heavy 140-test suite times out even at a 1800s cap. Verified instead two
ways: (1) live-path HTTP (real route + auth + editor render, ephemeral SX_SERVING_JIT=1),
(2) a focused in-process eval of the create-relation core (exists/is-a/kind-spec/symmetric/
registry-len = true,true,true,true,5). Prior full run was 140/140; changes since are purely
additive (handler + form + route + 3 tests). Re-run the blog suite when the box is quiet.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

plans/relations-as-posts.md

@@ -156,12 +156,16 @@ type — `:editor` if set, else the generic form. Same decidable-core / fenced-f
 declarative form covers the 95%, a code component handles the cases that need real interaction.
 
 **Refined build order** (this is what `/meta` is the on-ramp to):
-1. `/meta` overview — DONE (the *see*; `host/blog-type-defs` + `host/blog-meta-index`).
-2. **Slice 8 — typed fields** `{name, value-type, widget}` on a type — the **keystone** (drives form + template).
-3. **Generic instance form** — input per field ("the editor maps onto types").
-4. **Render template per type** — data, field-placeholders.
-5. **Cards-as-types + migrate** — seed the card-type vocabulary from content-on-sx; type the old posts.
-Plus the editor surfaces on `/meta`: **create-type** / **create-relation** forms, then **clear-and-reseed**.
+1. `/meta` overview — **DONE + LIVE** (the *see*; `host/blog-type-defs` + `host/blog-meta-index`).
+2. **Slice 8 — typed fields** `{name, value-type, widget}` — the keystone — **DONE + LIVE**.
+3. **Generic instance form** — input per field ("the editor maps onto types") — **DONE + LIVE**.
+4. **Render template per type** (8c) — data, `(field "name")` placeholders — **DONE + LIVE**.
+5. **Cards-as-types + migrate** — seed the card-type vocabulary from content-on-sx; type the old posts — NEXT.
+Editor surfaces on `/meta`: **create-type** (`POST /meta/new-type`) — **DONE + LIVE**; **create-relation**
+(`POST /meta/new-relation`) — **DONE, but SESSION-SCOPED**: the relation-post + edges persist, the
+rel-kinds registry entry is a runtime concat lost on restart (boot loader can't dynamically enumerate
+under JIT-at-boot — the kernel boot-resolver gap, flagged to sx-vm-extensions). Then **clear-and-reseed**.
+Also open: **specialised editors** (`:editor` slot → content-addressed component, e.g. WYSIWYG).
 
 ## Behaviour as data — lifecycles + ECA over an effect vocabulary (DESIGN — Slice 9)