fix(button): remove redundant data-state enum (book §1 purity)

Audit 2026-05-27 caught 11 `data-state="idle"` violations across 3
disclosure trigger components (dropdown-menu, table.row-detail-trigger,
tree-grid.expand-trigger). Root cause was composition: each used
`<Button>` as its chrome via `{...props}` spread, and Button's morfo
declared a redundant `data-state ∈ [idle, loading]` enum that the
runtime emitted unconditionally — clobbering the outer trigger's
`data-state="open|closed"` via mergeProps order.

Doctrinal fix: REMOVE `data-state` from Button's morfo entirely.
Button's loading state is already fully expressed by the
`data-loading` presence flag (declared further down in the same morfo
and consumed by eidos as `[data-loading]`, not
`[data-state='loading']`). The 'idle' value was a redundant synonym
for "not loading" — and the book canon favours "presence = active
state, absence = rest" for binary states (cf. `data-disabled`,
`data-loading`).

**Book-pure rationale**:
- Disclosure (family `emerge`): `data-state ∈ [open, closed]` —
  dialog, drawer, popover, accordion, dropdown-menu, etc.
- Lifecycle (family `sustain`): `data-state ∈ [idle, loading, ...]` —
  image, avatar, button (until now), card, field.
- Mixing the two vocabularies in a single attr is the incoherence
  this fix removes.
- Button is interactive surface, NOT lifecycle: its "rest" is
  natural absence of `data-loading`, not a distinct `idle` state.

**Result**:
- `npm run morfo:check`: 16 issues / 6 components → **6 issues / 3
  components**. Removed all 11 `'idle'` violations.
- Composition pattern restored: `<Button>` no longer clobbers
  `data-state` on the host trigger.
- Eidos CSS unchanged (already uses `[data-loading]`).
- Tests: 803/801 unchanged (2 remaining failures are unrelated, in
  the user's words editor WIP).

**Not fixed in this commit** (3 remaining `morfo:check` failures):
- `avatar.provider`: missing `data-color` emission (4×)
- `color-picker.provider`: missing `data-state` emission
- `date-picker.provider`: `data-kind="date"` not in declared
  `[day, month, year]` enum.
Each requires a separate domain decision.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/uix/morfo/components/button.ts

@@ -81,13 +81,23 @@ export const buttonMorfo = {
 			kind: 'public',
 			defaultElement: 'button',
 			optional: false,
+			// Button's loading state is fully expressed by the `data-loading`
+			// presence flag (declared below) — eidos CSS already uses
+			// `[data-loading]`, NOT `[data-state='loading']`. The morfo
+			// previously declared a redundant `data-state ∈ [idle, loading]`
+			// enum that:
+			//   (a) duplicated `data-loading`
+			//   (b) emitted `data-state="idle"` on every non-loading button,
+			//       which CLOBBERED the host disclosure's `data-state="open|closed"`
+			//       whenever Button was used as the chrome for a
+			//       RowDetailTrigger / ExpandTrigger / DropdownMenu Trigger
+			//       (audit 2026-05-27 caught this).
+			// `data-state` removed entirely. The book doctrine favours
+			// "presence = active state, absence = rest" for binary states
+			// (data-disabled, data-loading). 'idle' is not a value — it's
+			// the natural rest where no flag is emitted.
 			states: ['idle', 'loading'],
 			data: [
-				{
-					attr: 'data-state',
-					values: ['idle', 'loading'],
-					value: v.stateRef('loading')
-				},
 				{
 					/**
 					 * Resolved visual color. Per doctrine, when intent is