host: revert legacy-editor shims — clean over fancy, 181/181

Pull out the debt that revived the legacy editor: removed kg-compat.sx (uncommitted
bare->namespaced kg-card aliases), the ./blog container mount, the legacy
sx-editor.js + hardcoded asset URLs + ~editor/sx-editor-styles reuse at /new, and
the blog/sx preloads. /new is now a clean minimal form.

Finding that reshapes Phase 5: render-page (5.1) renders STATIC component trees
but is NOT the full evaluator — a component with a data loop ((map fn items) over
(unquote data)) errors 'Not callable: nil'. So clean dynamic component pages + a
native island editor need the aser SSR pipeline (5.2), not just render-page.

Posts still render via per-block guarded render-page; unsupported editor cards
(~kg-md) show placeholders by design (no alias shim). All endpoints 200, boot clean.

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

plans/host-on-sx.md

@@ -228,9 +228,21 @@ Sub-steps (each independently gated/verified):
       mangling). Root cause confirmed: bare render-to-html on an *evaluated* tree
       mangles attrs; `render-page` renders the *unevaluated* expr so expansion +
       attr-collection happen in render-to-html.
-- [ ] **5.2 Shell statics in the host env.** Run `http_inject_shell_statics` for
-      the host's loaded components so the shell can inline defs/CSS/asset-hashes.
-      Gate: a full page shell emits with component defs inlined.
+- [ ] **5.2 Shell statics + aser SSR (the real dynamic-page path).** `render-page`
+      (5.1) renders STATIC component trees, but is NOT the full evaluator —
+      dynamic-logic bodies fail (proven: a component doing `(map fn items)` over
+      `(unquote data)` → "Not callable: nil"). Clean dynamic component pages
+      (a posts loop) + island pages therefore need the **aser** pipeline (evaluate
+      control flow, serialise tags) + `http_inject_shell_statics` (component defs /
+      CSS / asset hashes) + `~shared:shell/sx-page-shell`. Gate: a page with a data
+      loop renders, and a full shell emits with defs inlined.
+      NOTE (2026-06-19): the legacy-editor stopgaps (kg-compat aliases, `./blog`
+      mount, legacy `sx-editor.js` + hardcoded asset URLs at `/new`, the
+      `~editor/sx-editor-styles` reuse) were REVERTED — they were debt to revive
+      stale code. `/new` is now a clean minimal form; host pages still use minimal
+      shell HTML until the aser path lands. Posts render via per-block guarded
+      `render-page`; unsupported editor cards (e.g. `~kg-md`) show placeholders by
+      design (no alias shim).
 - [ ] **5.3 Static-asset serving.** Serve `/scripts/*.js`, `/*.css`, `/wasm/*`
       from `shared/static`. Host has none today — needs a kernel file-serving
       route in the `http-listen` server (or a file-read prim + SX static handler).