docs: archive the finished backlogs (RD-30)

Two backlog trees are complete: `docs/project/backlog/` (75 files, every
WP done) and `docs/project/refactor-backlog-setup/` (the arc before it).
Move both under `docs/project/archive/` with `git mv`, so history stays
intact through `git log --follow`. `SHOWCASE-ROADMAP.md` moves with them,
because it points at the now-archived backlog README.

Add `docs/project/archive/README.md`. It states that these trees are
historical and names the two directories that are still live.

Repoint every inbound reference named in RD-30's Files table: CLAUDE.md,
the root README, both backend READMEs, `LetterHtml.cs`, `a11y.mdx`, the
`document-feature` and `new-ssp` skills, and the readable-codebase PLAN,
README, and RD-19 ticket. Fix two upward-relative links inside the moved
WP files (WP-68, WP-69) that gained a directory level and would otherwise
break. Repoint `.prettierignore`'s two agent-prompt exclusions to their
new path, so prettier keeps leaving those files' exact wording alone.

Mark RD-30 done and check off its acceptance criteria; flip its README
row to done.

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

docs/project/archive/backlog/WP-43-scaffold-generators.md

@@ -0,0 +1,47 @@
+# WP-43 — Runnable leaf generators
+
+Status: done (value-object + form-machine; ui-component/bff-endpoint kept as skills)
+Phase: 8 — platform/DX/showcase
+Priority: P3
+
+## Outcome
+
+Tool = **plop**. `plopfile.mjs` + `plop-templates/` provide two runnable generators for the pure-TS
+patterns: `npm run gen:value-object` (branded type + `parseX` + spec, mirrors postcode/bsn) and
+`npm run gen:form-machine` (Draft/Valid/Errors + Editing/Submitting/Submitted/Failed union +
+`initial`/pure `reduce`/`assertNever` + spec, mirrors change-request.machine). Prompts take
+context + PascalCase name (positional-arg bypass for scripting); each emits a co-located spec so the
+"pure logic must have a spec" rule holds by default; a post-action reminds to add the English
+`<target>` for the generated `$localize` id. Smoke-tested (both generate → lint + dep:check clean),
+then the demo output removed. Skills (`value-object`, `form-machine`) point at the generator.
+`plop-templates/` is prettier-ignored (Handlebars, not TS).
+
+**Scoped out (kept as skills):** `gen:ui-component` (Angular template `{{ }}` collides with
+Handlebars) and `gen:bff-endpoint` (spans the C# backend + `gen:api` regen) — a generator adds
+little over the recipe there.
+
+## Why
+
+The house patterns (value object, form machine, bff endpoint, ui component) are documented only as
+agent-executed prose skills; there's no `npm run gen:*` a developer runs to emit the boilerplate.
+For a template meant to bootstrap real registers, mechanise the highest-churn recipes.
+
+## Decisions
+
+- **Step 1 — tool fork:** plop (recommended: tiny, readable templates, `npm run gen:*`) vs Angular
+  schematics (native `ng generate`, heavier to author). Decide before building.
+- Generators emit house-pattern files **with co-located spec/story**, matching current idioms:
+  `gen:value-object`, `gen:form-machine` (page/wizard), `gen:bff-endpoint`, `gen:ui-component`.
+- Templates become the single source; each matching skill gets a one-line "run `npm run gen:x`, then …".
+
+## Files
+
+- New `plopfile.mjs` (or `schematics/`) + template files; `package.json` `gen:*` scripts.
+- Update the corresponding `.claude/skills/*/SKILL.md` to invoke the generator.
+
+## Acceptance criteria
+
+- [x] `gen:value-object` + `gen:form-machine` emit files that pass `npm run lint` + `dep:check`
+      with no hand-edits beyond the domain specifics (rule/fields) + the en.xlf target.
+- [x] Generated units include their co-located spec.
+- [x] Smoke-tested both; `npm run ci` green.