feat(toast): explicit persistence: 'transient' on signal-announce event

Documents the deliberate choice to keep the announce event's perceptual
projection transient even though the canonical book §6.2 table would
suggest `untilFix` for `signal + risk` or `untilAction` for `signal + threat`.

Rationale: the Toast component owns its own lifecycle via
`Toast.Provider`'s auto-dismiss timer + user dismiss. The `data-event-*`
projection is a one-shot pulse when the toast enters. Persistence of the
toast surface itself lives in `data-state` (open/closed) on the Item,
not in the signal projection.

Found via audit of all `verb: 'warn' | 'alert' | 'notify'` events across
`src/uix/morfo/components/*`. Toast was the only one without an explicit
persistence declaration — annotated now so the choice is intentional
rather than implicit-default.

(`words.signal-invalid-input` also lacks persistence but it belongs to
the in-flight words editor work tracked separately by the user.)

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

src/uix/morfo/components/toast.ts

@@ -21,6 +21,14 @@ export const toastMorfo = {
 			}
 		},
 		{
+			// Persistence: explicit `transient` even though the book §6.2
+			// canon would imply `untilFix` / `untilAction` for `signal +
+			// risk` / `signal + threat`. The Toast component owns its own
+			// lifecycle via `Toast.Provider`'s auto-dismiss timer + user
+			// dismiss; the `data-event-*` projection is a one-shot pulse
+			// when the toast enters. Persistence of the toast surface
+			// itself lives in `data-state` (open/closed) on the Item, not
+			// in the signal projection.
 			name: 'announce',
 			semantic: {
 				family: 'signal',
@@ -31,7 +39,8 @@ export const toastMorfo = {
 					fromProp: 'intent',
 					default: 'neutral',
 					supported: INTENTS
-				}
+				},
+				persistence: 'transient'
 			}
 		},
 		{