fix(scaffolding): rename create-ssp to create-frontend, fix 2 bugs it surfaced

Renamed scripts/create-ssp.mjs -> create-frontend.mjs (+ its WP-45 doc, npm
script, and every prose/command reference) since "ssp" reads as an acronym
where "create-frontend" says what it does.

Also fixes two real bugs found while running it for real during WP-61:
scripts/ci-local.sh was missing from RENAME_CONTENT_FILES (any --name'd
clone that keeps a backend would break `npm run ci`, still hardcoding
BigRegister.slnx), and plopfile.mjs's `gen:context` insertion into
.dependency-cruiser.js anchored on the `showcase: null,` line, which
create-ssp/create-frontend has already stripped by the time gen:context
runs in the same invocation — silently leaving a freshly scaffolded
context with no CONTEXT_ALLOWED fence entry at all. Re-anchored on the
`const CONTEXT_ALLOWED = {` line instead, which never moves.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/reference/scaffolding.md

@@ -71,7 +71,7 @@ step-by-step and its GREEN-at-every-step verify gate.
 
 - **`gen:context`** ([WP-44](../project/backlog/WP-44-context-generator.md)) — a runnable
   version of the `new-context` skill. Planned, not shipped.
-- **`create-ssp`** ([WP-45](../project/backlog/WP-45-create-ssp-generator.md)) —
+- **`create-frontend`** ([WP-45](../project/backlog/WP-45-create-frontend-generator.md)) —
   mechanised `new-ssp`. Planned, not shipped.
 
 Don't assume either command exists — use the corresponding skill until they land.