Chart builder: field-first shelf + value-or-field channels

docs/chart-builder-enhancement-scope.md

@@ -25,6 +25,29 @@
 Newest first. The at-a-glance build-order tracker is §4; per-item detail is §3. This log is
 the quick "where are we" — read it first.
 
+- **2026-06-11 (Phase 2)** — **2A + 2B shipped: the field-first interaction substrate.** Up next: **3A intent-first front door**.
+  - **2A · Value-or-field channels (the Property model).** `ChannelMapping` gained a constant
+    `value` arm; the assembler emits `{ value }` and the measure/stack/area-split/prune logic
+    all treat a constant Colour as "no series." New pure helpers (`isValueMapping`,
+    `channelAcceptsValue`, `defaultChannelValue`, `coerceChannelValue`,
+    `isColumnAllowedOnChannel`). `type` stays required (a constant carries a preserved-but-
+    ignored type, so a field↔constant toggle round-trips). Tested.
+  - **2B · Field-first builder.** The channel-first dropdown rows are replaced by a **field
+    shelf** (columns as type-glyphed chips, auto Dimensions/Measures split past a column
+    threshold), **click-to-assign** (armed channel, else first empty that accepts it —
+    `assignField`/`focusChannel`), Tableau-style **pills** (a type chip that **cycles** the
+    field type in-place, transforms beneath), and the **on-chart Columns/Rows shelves** above
+    the preview (X/Y as a property of the chart) with a **reserved faceting placeholder** in
+    each. Colour/Size live in a left **Marks card**, each switchable to a **constant** (2A).
+  - **Decisions taken (overridable):** drag deferred (click/keyboard-first, fully tested);
+    field grouping auto; aggregate stays a control under the pill (no pill context-menu yet).
+  - **Spec §06** rewritten for the field-first model (Layout, Encoding channels, faceting
+    placeholder, constants, validation/output).
+  - **Verified:** `typecheck` + `test` (762, +20 core/store/modal) + `eslint` + `build`.
+    **Owed:** a manual/visual pass against the live builder; a **`/council`** look at the
+    type-cycle chip (a cycling button gives no direct type pick — explicit menu vs cycle is a
+    real a11y trade-off) and the constant affordance.
+
 - **2026-06-11 (later)** — **Owed debts on the Data section closed. Up next: Phase 2 (2A value-or-field channels, then 2B field shelf).**
   - **Council pass** on the new error/disclosure copy (the previously-deferred auto-fire
     surface). Three a11y conformance gaps against `architecture/10` were fixed: the inline
@@ -393,9 +416,9 @@ Phase 1  1A actionable hints      ✓ done
          1C filter (+ calculate)  ✓ done
          1D data preview          ✓ done
          1E expr-validate         ✓ done (syntax + unknown-field; completion popup deferred)
-Phase 2  2A value-or-field channels (Property model)  ← next
-         2B field shelf + in-place type cycling   ← Tier-C substrate
-Phase 3  3A intent-first front door (Tier C)       ← built on 2B; the defining feature
+Phase 2  2A value-or-field channels (Property model)  ✓ done
+         2B field shelf + in-place type cycling       ✓ done (field-first + on-chart shelves)
+Phase 3  3A intent-first front door (Tier C)       ← next; built on 2B; the defining feature
          3B starter examples
 Phase 4  (gated) theta/facets/styling-overrides/undo/lookup — decide after Phase 3