refactor(ssr): Phase 4 — full Selmer migration of POS Sales Summary; remove the wizard; fix add-item + totals

Migrates the POS Sales Summary edit modal off the wizard to a plain Selmer form,
building on the parity gate committed earlier. Largest migration so far and the
first with no prior test coverage.

What changed
- Wizard removed: deleted MainStep/EditWizard records, MultiStepFormState, the
  step-params[...] prefix, the EDN snapshot round-trip, and all mm/* middleware.
  Replaced with a plain handler + flat wrap-decode/wrap-derive-state. The 51 fc/
  cursor refs are de-cursored into explicit data + Selmer templates.
- db/id-keyed item merge: wrap-derive-state overlays posted items onto the
  persisted items by :db/id, so read-only fields the form doesn't post
  (ledger-side, amount) survive a re-render and the debit/credit split + totals
  stay correct. New manual rows (temp db/id) ride through as-is.
- Inline click-to-edit account cell preserved as three small targeted
  .account-cell-swap routes (edit/save/cancel-item-account), ported to Selmer
  with the new field-name scheme.
- 100% Selmer modal render path (the remaining Hiccup / hx-swap-oob / "hx-"
  strings are all grid-page code — grid render lambdas, the filters form, and the
  submit response-header map — not the modal).
- Routes: dropped edit-wizard-navigate + new-summary-item; added form-changed.

Fixes (two pre-existing bugs, per request)
- "New Summary Item" add button (was throwing `newRowIndex is not defined` and
  targeting a non-existent `.new-row`) is now a whole-form-swap op=new-item that
  adds an editable manual row (category + account typeahead + debit/credit money
  inputs + remove).
- The dead totals/balance display (malformed Hiccup that discarded its labels) is
  replaced by a proper #summary-totals block showing running Total +
  Balanced/Unbalanced, refreshed via a Rule-4 targeted swap on manual amount edits.

Scorecard delta (pos/sales_summaries.clj): LOC 790->732, mm coupling 20->0,
wizard records 4->0, fc/ cursor 51->0, step-params 27->0 (2 comments), modal
routes 8->6. (hx-swap-oob 1 and mixed-hx live in the grid page, not the modal.)

Verification: sales-summary spec 7/7 (incl. the two fixes); full Playwright suite
46/46; cljfmt clean. Skill fed: scorecard row + narrative; gotchas (parity-gate-
first, characterize-then-fix, keyup-trigger tests); cookbook (inline click-to-edit
cell, db/id-keyed item merge).

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

resources/templates/sales-summary/edit-form.html

@@ -0,0 +1,4 @@
+{# Plain sales-summary edit form (no wizard). db/id rides in a hidden field; all other
+   state is the live form, re-derived against the entity each request (no EDN snapshot,
+   no step-params). #}
+<form id="summary-edit-form"{{ form_attrs|safe }}><input type="hidden" name="db/id" value="{{ db_id }}">{{ modal|safe }}</form>

resources/templates/sales-summary/summary-body.html

@@ -0,0 +1,4 @@
+{# Sales-summary modal body: a read-only Debits | Credits two-column view of the auto
+   items (each account is inline-editable), a swappable totals/balance block, and an
+   editable Manual Items section with a working "New Summary Item" add. #}
+<div class="space-y-4 p-2"><div class="grid grid-cols-2 gap-6"><div><div class="font-semibold text-sm mb-2">Debits</div><div class="space-y-1">{{ debit_rows|safe }}</div></div><div><div class="font-semibold text-sm mb-2">Credits</div><div class="space-y-1">{{ credit_rows|safe }}</div></div></div><div id="summary-totals">{{ totals|safe }}</div><div class="mt-4 border-t pt-3"><div class="font-semibold text-sm mb-2">Manual Items</div><div class="space-y-2" id="manual-items">{{ manual_rows|safe }}</div><div class="mt-2 flex justify-center">{{ new_item_button|safe }}</div></div></div>