docs: teach the effect map, not the deleted submit method (RD-09)

RD-05 through RD-08 replaced the hand-called submit method with
createStore's effect map. Two teaching documents still showed the old
method in a code block, as the answer to "how does a submit happen?".
Both blocks also called a function that no longer exists.

Rewrite the code block in ARCHITECTURE.md section 2d and its
fp-tea-atomic-design.md counterpart. Both now show the effect map, keyed
on the Submitting tag, using the same herregistratie worked example with
its optimistic begin/confirm/rollback calls. Both use draftSync.submit,
the call the two herregistratie wizards make today.

State the two properties the old idiom lacked, since they are the reason
for the change: entering a state runs its effect, so a dispatch cannot
skip it; and double-submit protection is structural, because the effect
fires only on a tag transition. Add one sentence on the Seed exemption: a
mount or restore message must not trigger a submit.

Fix the one runIfSubmitting() hop in the write walkthrough at
ARCHITECTURE.md's line 574. The rest of section 6a stays stale on
purpose — RD-31 owns it, including its line citations and dead paths.
fp-tea-atomic-design.md's broken pre-monorepo paths stay stale too —
RD-32 owns those.

Set RD-09's Status to done and its README row to done in the same
commit.

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

docs/project/readable-codebase/RD-09-docs-effect-idiom.md

@@ -0,0 +1,132 @@
+# RD-09 — Update the two documents that teach the deleted submit idiom
+
+Status: done
+Source: PLAN.md 1c (A5, as corrected)
+
+## Why
+
+RD-05 through RD-08 replaced the hand-called `runIfSubmitting` with `createStore`'s effect
+map, and `grep` now finds the method nowhere in `apps/` or `libs/`. Two teaching documents
+still present it as the house idiom, in a code block, as the answer to "how does a submit
+happen?".
+
+Both blocks are doubly stale: they teach a deleted idiom **and** call
+`submitHerregistratie(s.data)`, a function that no longer exists either.
+
+A document that teaches a deleted idiom is worse than no document — a reader who follows it
+reintroduces the silent-failure bug RD-06 fixed.
+
+## Read first
+
+- `libs/shared/src/application/store.ts` — the effect map, the trigger rule, the `Seed`
+  exemption, and the "must never throw" contract. This is the new idiom to document.
+- Any migrated call site, as a worked example — `besluit-form.component.ts` is the smallest.
+- `docs/reference/architecture/ARCHITECTURE.md` §2d (the block at 306-322) and the write
+  walkthrough mention at :574.
+- `docs/reference/fp-tea-atomic-design.md` (the block at 336-350).
+
+## Decisions (pre-made, don't relitigate)
+
+1. **Scope is exactly two documents.** An earlier version of this plan claimed
+   `plop-templates/form-machine.hbs` generates `runIfSubmitting` and that
+   `.claude/skills/form-machine/SKILL.md` teaches it. **Both are false**, verified by grep:
+   the plop template is machine-only (74 lines, no `@Component`), and the skill never mentions
+   it. Do not "fix" either file. If you find yourself editing a `.hbs` or a `SKILL.md`, stop.
+
+2. **Rewrite the code block, do not delete the section.** §2d ("Side effects (HTTP) without
+   polluting the reducer") and its fp-tea counterpart answer a real question and answer it
+   well. The answer changed; the question did not.
+
+3. **The new block shows the effect map.** Same worked example (a herregistratie submit with
+   its optimistic `begin`/`confirm`/`rollback`), expressed as a registration:
+
+   ```ts
+   private store = createStore<WizardState, WizardMsg>(initial, reduce, {
+     Submitting: async (s, store) => { … },
+   });
+   ```
+
+   Keep the numbered inline comments — they are what makes the block teachable.
+
+4. **State the two properties the old idiom lacked**, because they are the reason for the
+   change and a reader should see them:
+   - Entering the state runs the effect. A `dispatch` cannot silently skip it.
+   - Double-submit protection is structural: the effect fires only on a tag **transition**, so
+     a second `Submit` while already submitting is a reducer no-op and fires nothing.
+
+5. **Document the `Seed` exemption where the idiom is taught**, in one sentence: a mount or
+   restore message must not trigger a submit. That is the non-obvious part of the rule, and
+   `store.ts` explains it in full for anyone who needs more.
+
+6. **Fix `ARCHITECTURE.md:574`'s write walkthrough** too — it opens with `runIfSubmitting()
+(§2d) → createSubmitChangeRequest`. Replace the first hop with the effect map. Leave the
+   rest of §6a alone: **RD-31 rewrites that section**, including its stale `L<n>` citations and
+   two dead file paths. Touch only the `runIfSubmitting` hop here.
+
+7. **Drop the `submitHerregistratie(...)` call from both blocks.** That module no longer
+   exists (`submit-herregistratie.ts` was deleted). Use `draftSync.submit(...)`, which is what
+   the two herregistratie wizards actually call today.
+
+## Files
+
+- `docs/reference/architecture/ARCHITECTURE.md` (§2d block, and the one hop at :574)
+- `docs/reference/fp-tea-atomic-design.md` (the block at 336-350)
+
+No code files. No `.hbs`. No `SKILL.md`.
+
+## Steps
+
+1. Rewrite `ARCHITECTURE.md` §2d's code block per decisions 3-5.
+2. Fix the first hop of the write walkthrough at :574 per decision 6.
+3. Rewrite the equivalent block in `fp-tea-atomic-design.md` per decisions 3-5 and 7.
+4. Update this ticket's `Status:` to `done` and the README's RD-09 row to `done`.
+5. Commit all of it together.
+
+## Acceptance criteria
+
+The deleted idiom is no longer taught anywhere:
+
+```bash
+grep -rn "runIfSubmitting\|runIfIndienen" docs/ apps/ libs/ .claude/   # MUST return nothing
+grep -rn "submitHerregistratie" docs/                                  # MUST return nothing
+```
+
+Every code identifier the new blocks name must exist:
+
+```bash
+grep -n "StoreEffects\|effects?" libs/shared/src/application/store.ts   # the API is real
+grep -rn "draftSync.submit" apps/ssp | head -3                          # the call is real
+```
+
+```bash
+npm run ci   # exits 0
+```
+
+## Verification
+
+`npm run ci`. This ticket touches only two Markdown files under `docs/reference/`, so
+`--full` is not required — neither is globbed by Storybook.
+
+Read both rewritten blocks end to end and check a reader could follow them without opening
+`store.ts`. That is the actual acceptance test for a teaching document, and no command
+checks it.
+
+## Out of scope
+
+- The rest of `ARCHITECTURE.md` §6a — its stale `L<n>` line citations, its two non-existent
+  file paths, and its post-RD-16 `parseDashboardView` claim. **RD-31.**
+- `fp-tea-atomic-design.md`'s 11 broken pre-monorepo `src/app/…` paths and its broken anchor.
+  **RD-32.**
+- `plop-templates/form-machine.hbs` and `.claude/skills/form-machine/SKILL.md` (decision 1).
+- CLAUDE.md. **RD-33.**
+
+## Risks
+
+- **Do not chase the other staleness in these two files.** Both are also targets of RD-31 and
+  RD-32. Editing their line citations or paths here creates a conflict with those tickets for
+  no gain. Change only what teaches the submit idiom.
+- **`fp-tea-atomic-design.md`'s surrounding paths are already broken** (they use the
+  pre-monorepo `src/app/…` prefix). Leaving them broken in this commit is correct — RD-32 owns
+  them. Do not half-fix the file.
+- **Prettier formats Markdown.** Run `npx prettier --write` on both files, or `format:check`
+  fails.