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>

.claude/skills/ssr-form-migration/reference/scorecard.md

@@ -44,6 +44,9 @@ Each migration appends one row (after-numbers), referencing the before in the di
 | 3 | Transaction Bulk Code `transaction/bulk_code.clj` | 506 (was 420 — see exception) | **3** | 0 | 0 | **0** | 0 | 0† | reused **all** of Phase-2's `sc/*` lib + `account-typeahead*`/`location-select*` + `edit-modal`/`transitioner` chrome / added **`sc/select`** |
 
 † The one `"hx-..."` string hit is a response-header map (`{"hx-trigger" "refreshTable, reset-selection"}`), not a mixed attribute encoding. mm coupling 19→**0**, wizard records 3→**0**, step-params 10→**0** (the 2 hits are comments), Hiccup-in-render → **0** except the shared `com/success-modal` (heuristic-9 exception, as in Phase 2).
+| 4 | POS Sales Summary `pos/sales_summaries.clj` | **732** (was 790) | **6** modal | 0 | 0 | **0** | 1✦ | 0✦ | reused `sc/*` lib + `edit-modal`/`transitioner` chrome / added the inline click-to-edit **account-cell** + **manual-items** patterns |
+
+✦ The residual 1 `hx-swap-oob` and the `"hx-..."` string hits all live in the **grid page** code (the `grid-page` render lambdas + the `filters` form + the submit response-header map) — none are in the migrated **modal** render path, which is 100% Selmer. `defrecord` count **0** (all 4 wizard records gone), `fc/` cursor refs 51→**0**, mm coupling 20→**0**, step-params 27→**0** (2 comments). LOC dropped (this wizard held real custom code, unlike bulk-code's thin shell). **Two pre-existing bugs fixed** (per the user's call): the "New Summary Item" add button (was throwing `newRowIndex is not defined`) and the dead totals/balance display.
 
 ### New heuristics introduced at 2-final (full Selmer)
 
@@ -108,3 +111,25 @@ Each migration appends one row (after-numbers), referencing the before in the di
 > (resolve the non-editable selection to a concrete id vector at open, ride it in hidden
 > fields — the bulk analog of edit's single `db/id`), and the **`:id`-keyed vendor typeahead**
 > (a value-bound hidden must be keyed or its posted value goes stale across a whole-form swap).
+
+> **Phase 4 — POS Sales Summary (first modal with no prior test coverage).** The largest
+> migration so far and the first that required **building the parity gate first**: the modal
+> had zero e2e/clj tests and the test server seeded no POS data, so the work began by seeding a
+> balanced sales summary + writing a 7-test characterization spec (committed separately, ahead
+> of the rewrite). Then the standard wizard→plain-Selmer migration: `MainStep`/`EditWizard` +
+> `MultiStepFormState` deleted, the 51 `fc/` cursor refs de-cursored into explicit data +
+> Selmer, `step-params` dropped, the EDN snapshot replaced by flat `wrap-decode`/`wrap-derive-state`
+> (with a **db/id-keyed item merge** so the read-only fields the form doesn't post —
+> ledger-side, amount — survive a re-render). The **inline click-to-edit account cell** (pencil →
+> typeahead editor → check/cancel) was preserved as three small targeted `.account-cell`-swap
+> routes (a distinct feature, not folded into the form-changed dispatcher). LOC 790→**732** (net
+> ↓ — a fat wizard, opposite of bulk-code).
+>
+> **Characterize-then-fix.** Writing the gate surfaced two pre-existing bugs: the "New Summary
+> Item" button threw `newRowIndex is not defined` (dead since forever) and the totals/balance
+> display was dead code (malformed Hiccup that discarded its labels). The spec first *documented*
+> them as broken (never assert a bug as working); then, on the user's call, the migration **fixed
+> both** — add-item is now a whole-form-swap `op=new-item` adding an editable manual row, and a
+> proper `#summary-totals` block shows running Total + Balanced/Unbalanced (a Rule-4 targeted swap
+> on manual amount edits). The spec was updated to assert the fixed behavior. New cookbook entries:
+> the **inline click-to-edit cell** and the **db/id-keyed item merge** for partially-posted rows.